The strength of sponsored blog posts

An experiment on the effects of blogger popularity, degree of disclosure and the mediating role of credibility on consumer’s purchase intention.

Inge Hoeks ANR: 196930

Master thesis Communication and Information sciences Track Business Communication and Digital Media

School of Humanities Tilburg University, Tilburg

Mentor: dr. A. P. Schouten Second reader: dr. C.C. Liebrecht

22 August 2016 THE STRENGTH OF SPONSORED BLOG POSTS

Abstract

The rapidly expanding blogosphere has caused a small group of popular and influential bloggers to become celebrities. Leading brands use this growing popularity by collaborating with these popular bloggers to represent, promote or endorse their products. A sponsored collaboration with a blogger can be valuable for brands, based on the belief that the opinions of bloggers are very influential and have high persuasive impacts on their readers. However, since national regulations oblige bloggers to reveal any sponsored collaboration with a brand, the commercial intent of those blog posts can no longer be hidden. Therefore, bloggers are obliged to disclose the sponsored relationship with brands. However, the effect of the degree of this disclosure on purchase intention of the reader is still unknown. This study made use of a 2 (blogger popularity) x 3 (degree of disclosure) experimental design and gathered a total of 235 participants to examine consumers’ purchase intention and perceived credibility of the source. The results showed that the sponsoring of blog posts and the popularity of the blogger did not significantly affect consumer’s purchase intention. However, when comparing the sponsored conditions, moderate disclosure lead to a higher consumer’s purchase intention compared with complete disclosure.

Keywords: Sponsored blog posts; Purchase intention; Blog posts; blogger popularity

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Introduction

Blogs have captured the world’s attention (Chu & Kamal, 2008). In May 2015 the Dutch newspaper Het Financieel Dagblad used the following headline, “Supermodels face competition from popular bloggers and Youtube-stars”, for an extensive article about the meteoric rise of bloggers as brand ambassadors (Smit, 2015). The article stated that catwalk models and celebrities have to make room for the new heroes of the internet, bloggers. They are considered to be the new stars of this era (Smit, 2015). Additionally, statistics reveal that in 2014, 6.7 million people worldwide use blogging sites to blog, 77 percent of internet users read blogs, and 23 percent of the internet time is spent on social media and blogs (Ignitespot, 2014). These numbers show that the growing attention for blogs is not without a reason. The growing popularity and rapid expansion of the blogging phenomenon is also shown by the fact that popular bloggers are looked at as celebrities. These bloggers have millions of regular visitors and have made their living out of blogging (Chiu & Ho, 2009). Harvard Business School even dedicated a case study to the founder of the world’s most popular fashion blog, The Blond Salad. The 27-year-old founder Chiara Ferragni has dozens of fans across the globe, a staff team consisting of fourteen members and revenues estimated at nine million dollars in 2015 (Keinan, Maslauskaite, Crener & Dessain, 2015). Weblogs, or in short blogs, belong to the new generation of the Web 2.0 and serve as a platform for users to create and share content (Fieseler, Fleck & Meckel, 2010). The so- called Web 2.0 enables users to not only to consume, but also to create content by composing, editing, modifying, and exchanging data (Chiu & Ho, 2009). Anyone can create a blog and post one’s own ideas, opinions, and various other forms of content on one’s website. Therefore, blogs are expected to be an important digital information source, because they contain large quantities of rich digital content (Chiu & Ho, 2009). Besides the creation of blogs, reading them has also become an important activity for Internet users. Popular blogs that are frequently visited and have millions of regular visitors are an important information source which consumers use to gather information. These blogs exert a major influence on consumer’s purchase behavior. Visitors develop a strong bond and close interpersonal relationships with the blog or blogger, by frequently visiting, reading, and exchanging information (Chiu & Ho, 2009). As a result, bloggers and their blogs are a powerful advertising medium and which results in a growing trend of blog advertising (Chiu & Ho, 2009; Zhu & Tan, 2007). Leading brands use this growing popularity by collaborating with popular bloggers to represent, promote or endorse their products (Chu & Kamal, 2008).

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In the literature, Zhu and Tan (2007) used the term blog advertising to refer to the paid sponsorship of bloggers to mention, review, promote or sell products in their blog posts. A sponsored collaboration with a blogger can be valuable for brands, based on the belief that the opinions of bloggers are very influential and have high persuasive impacts on their readers (Zhu & Tan, 2007). In fact, Hope (2002) stated that blogs with a brand-related message are perceived as highly credible, because bloggers are not dependent on corporate interests. Because of their impact, selecting appropriate blogs and proper use of those blogs is an important corporate advertising issue (Chiu & Ho, 2009). As blogs become a powerful advertising and communication medium, understanding the use of blogs and the importance of credibility is fundamental for marketers, companies, and brands (Chiu & Ho; Porter, Sweetser & Chung, 2009). Since national regulations oblige bloggers to reveal any sponsored collaboration with a brand, the commercial intent of those blog posts can no longer be hidden (Lu, Chang & Chang, 2014). Although the credibility of blog posts has extensively been researched, very little attention has been paid to sponsored blog posts (Colliander & Erlandsson, 2015; Lu, Chang & Chang, 2014). Do blog readers care at all if a blogger has been compensated for endorsing certain products or services? Previous studies have reported the influence of revealing the use of sponsored blog posts on purchase intention of readers, but have not dealt with the degree of disclosure about the sponsored relationship. It can be assumed, that the degree of disclosure about the sponsored relation between the blogger and a brand influences the credibility of the blogger and thereby the purchase intentions of the reader. Since sponsored recommendation posts are proven to be a successful marketing tool, understanding of how the type of mandatory disclosure can influence readers purchase intention appears to be crucial in understanding the use of this influential online medium. However, limited research has been conducted on blogs and their impact on consumer’s purchase intention (Bouhlel, Mzoughi, Ghachem & Negra, 2010; Chu & Kamal, 2008). Therefore, this study tries to gain insights in the blogging phenomenon and the use of blog marketing to expand the existing literature. Which in turn allows brands and marketers to make better use of this marketing tool. Moreover, this study investiges the effect of blog popularity. The small group of extremely popular bloggers are considered to be important influencers among consumers, because of their huge reach consisting of a loyal fan base (Trammel & Keshelashvili, 2005). However, given the nature of the blogosphere, influential and popular blogs are few (Agarwal, Liu, Tang & Yu, 2008). On the other hand, the number of relatively unpopular

4 THE STRENGTH OF SPONSORED BLOG POSTS bloggers continues to expand rapidly. Although these popular bloggers are becoming leading online influencers with a high publicity effectiveness, previous research has not dealt with the potential effects of differences in popularity. Therefore, this study also tries to identify to what extent blogger popularity influences consumers. Conclusively, the following research question will be answered:

Which effects have the popularity of a blogger and the degree of disclosure about the use of sponsored blog posts, on the credibility and purchase intention of blog readers?

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Theoretical Framework

Blogs as medium

Weblogs, mostly used as the abbreviation blogs, have gained immense popularity all over the world. Hansson (2015) describes a blog as a personal diary, where bloggers share their own thoughts, content, or ideas and which is accessible for others via the Internet. Chu and Kamal’s (2008) description adds that these strongly personalized diaries generally contain up-to-date content arranged in chronological order. Most of them are predominantly opinion-based and the largest demographic for this ‘personal diary’ genre blogs are females and teenagers (Schmidt, 2007). Most blogs make us of text, images, videos, links to other blogs and webpages or a combination of the above. The entries of these mentioned content forms are called blog posts (Agarwal, Liu, Tang & Yu, 2008). Researchers stated that blogs became immensely popular because they are easy and freely accessible, each blog has its own theme, they are updated regularly about contemporary topics, and written by everyday persons with which the reader can identify (Grossman, Hamilton, Buechner and Whitaker, 2004; Hansson, 2015). These features make blogs an important and reliable information source for readers. Literature defines three main types of blogs: personal journals, filters and notebooks (Trammel & Keshelashvili, 2005). Personal journals are blogs which contain the blogger’s thoughts, ideas and daily activities. Filter blogs contain links to content published by other authors which the blogger has found on the Internet and then put together. These blogs contain little content written by the blogger himself, but primarily news items and other contemporary topics. Lastly, the notebook blog contains lengthy stories, focused essays or opinion articles. Apart from the type of blog, the purpose or the content, blogs always consist of a virtual environment controlled by the author or authors (Trammel & Keshelashvili, 2005). According to Nardi, Schiano, and Gumbrecht (2004) bloggers have several possible reasons to engage in blogging and share their blog posts. For instance, bloggers express their opinions to influence their readers, and on the other hand, gain opinions and feedback from others. But also, updating others on their everyday lives, experiences, and thoughts. Each reason is linked to a certain audience, such as the blogger’s own personal acquaintances or just unknown readers beyond this group (Chu & Kamal, 2008). The magnitude of the blogging phenomenon ensures that influential and popular bloggers can make their blogs into a business and a make a living out of it. These bloggers

6 THE STRENGTH OF SPONSORED BLOG POSTS become stars and are considered to be celebrities in their own way, the most successful become their own brand within the blogging community. Most of today’s successful blogs started in the personal diary genre and grew from there into their current size and popularity (Lindquist, 2015). A relevant key feature of blogs is the ability to generate para-social interaction between bloggers and their readers (Colliander & Erlandsson, 2015). Para-social interaction is the illusionary experience of a face-to-face relationship with a media persona (e.g. bloggers) (Horton & Wohl, 1956). Unlike other media, bloggers often provide readers an insight in their daily life through pictures, personal stories or even videos. Para-social interaction strengthens and develops with each moment of contact with the blogger. After multiple interactions, stronger feelings will be developed and the reader may start to consider the blogger as a personal friend (Colliander & Erlandsson, 2015). Another important characteristic of a blog is that they allow direct and spontaneous interaction between the blogger and the reader (Bouhlel, Mzoughi, Ghachem & Negra, 2010). Readers are able to communicate directly with the blogger through the comment function, this allows readers to give their opinions, ask questions or provide feedback to the blogger. This two-way communication, the informal tone-of-voice, and the mentioned high para- social interaction may make bloggers important influencers for today’s web users (Lindquist, 2015). Due to these characteristics of blogs, bloggers potentially influence their readers’ attitudes and opinions to a large extent (Agarwal, Liu, Tang & Yu, 2008; Lindquist, 2015). Therefore, blogs may be more successful in influencing consumers than other traditional and online media sources or types of advertising (Lindquist, 2015; Zhu & Tan, 2007). This will be discussed in the next section.

Blog marketing Consumers use blogs among other things to publish and search for information about products and product experiences (Chiu & Ho, 2009). Theme blogs or other popular blogs are an important information source that consumers browse, adopt and trust. Thus, these frequently visited blogs often have a great influence on the purchase behavior of consumers (Chiu & Ho, 2009). Moreover, research demonstrated that consumers have more trust in peer consumers rather than companies and are more likely to trust information provided by fellow consumers to review products or services before making a purchase decision (Lee & Koo, 2012).

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The growing popularity and a vast reach make blogs a highly useful advertising tool for marketers, companies and brands (Tutaj & Reijmersdal, 2012; Zhu & Tan, 2007). Because of the degree of influence blogs have on consumer’s purchase decisions, it is interesting for brands to provide bloggers compensation in exchange for a favorable product review on their blog (Lu, Chang & Chang, 2014). This form of sponsoring will be discussed in a following section. In this study, blog marketing is defined as the paid sponsorship of bloggers to promote, sell or review products, services, brands, companies or other initiatives through blog content (Corcoran, Marsden, Zorbach & Röthlingshöfer, 2006; Zhu & Tan, 2007). Collaboration between brands and bloggers can be useful as bloggers are seen as influentials or opinion leaders. As said, bloggers have a vast reach with often a large and loyal fan base that admires them and sees the blogger as an inspiration. Therefore, bloggers are capable of influencing consumer’s opinion and attitude through their blogs and content (Freberg, Graham, McGaughey & Freberg, 2011). In addition, blogs have some advantages over traditional media channels, as bloggers can quickly react and respond to their readers or happenings, which is a benefit in fast moving businesses, for instance the fashion industry (Hauge, 2006). Moreover, previous research has proven that social media marketing can have a direct effect on purchase intention of consumers, which makes blogs and sponsored blog posts useful tools for marketers and companies (Bouhlel, Mzoughi, Ghachem & Negra, 2010; Hsiao Lu & Lan, 2013; Lindquist, 2015). Therefore, selecting appropriate blogs that match with the promoted product or service and proper use of those blogs to influence consumer’s purchase decisions, is an important corporate advertising issue (Chiu & Ho, 2009).

Purchase intention When consumers are considering to buy goods, they search for relevant information to weigh and evaluate different options. After these comparisons and judgements a consumer will engage in purchase behavior (Wang, Cheng, & Chu, 2013). The eventual purchase starts with an intention, therefore, research concerning consumer behavior mostly uses purchase intentions to measure consumer behavioral intention. A purchase intention is a consumer’s objective intention toward a product (Fishbein & Ajzen, 1975). As mentioned, blogs are possible information sources which can contribute to the formation of a purchase decision. The term purchase intention was defined by Spears and Singh (2004) as a consumer’s conscious plan or intention to make an effort to purchase a product. Previous studies suggest

8 THE STRENGTH OF SPONSORED BLOG POSTS that blogs can have a major influence on purchase intentions of consumers. In addition, Bouhlel et al. (2010) suggest that a consumer’s attitude toward a blog positively influences consumer purchase intention. This study thus proposes that blogs are important persuasive means which can influence consumer’s purchase intentions.

Blog credibility The perceived credibility of a blog is an important component in the persuasive impacts of sponsored blog posts. Research has demonstrated that the credibility of online information sources is important for Internet users (Sweester, Porter, Chung & Kim, 2008), as not many of them would rely on a source that is not perceived as credible (Kaye & Johnson, 2011). Kaye and Johnson (2011) state that people assess the credibility of personal blogs differently than other types of blogs like news or media. A number of researchers have reported that readers consider blogs as a more credible source, because they are a fair alternative for company-controlled blogs as they often contain a commercial or marketing intent (Flanagin & Metzger, 2007; Johnson & Kaye, 2004). In addition, bloggers often offer more up-to-date and genuine blogs because they are closer to the source than mainstream news sources, and therefore, are considered as more trustworthy (Kaye and Johnson, 2011; Zhu & Tan, 2007). Credibility models describe expertise and trustworthiness as the two most common key components of credibility (Chu & Kamal, 2008; Hovland, Janis, & Kelley, 1953). Expertise is described as the ability of a source to make valid claims, that is, the extent to which the source can make valid and accurate statements (Hovland, Janis, & Kelley, 1953). Trustworthiness refers to the belief of the reader that the source is providing information in an honest, fair, sincere, and honorable manner (Chu & Kamal, 2008). So far, blogs and their credibility have gained a lot of attention and have been intensively investigated (Bouhlel, Mzoughi, Ghachem & Negra, 2010; Chu & Kamal, 2008; Colliander & Erlandsson, 2015). However, the growth of the blogging phenomenon and the increased use of blog marketing caused changes in the blogging landscape. Although blog credibility has extensively been researched, previous research has not dealt with the effects of sponsoring and sponsored blog posts on this credibility. This study will therefore try to gain insights in the extent to which the use of sponsored blog posts influences the credibility of a blog post and the blogger.

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Sponsored posts

As mentioned, an effective form of marketing communication and blog marketing that has been operated by marketers is the recommendation of their product by others. An example of those sponsored recommendation posts are product reviews on blogs, as pointed out in an earlier section. Marketers can provide bloggers compensation in exchange for posting such a review on their blog (Lu, Chang & Chang, 2014; Zhu & Tan, 2007). This compensation may take many forms, for example monetary rewards, coupons, discounts, samples, or exclusive activity attendance (Sullivan, 2009). An earlier study defined sponsored blog posts as “a blog article written by a blogger who is sponsored by the producers of any product or by a marketing agency that reviews and promotes products and services on their blog” (Lu, Chang & Chang, 2014, p. 259). The sponsoring of bloggers is globally regulated by strict rules and legislations. Since the first of January in 2014, national Dutch regulations oblige bloggers to reveal any form of sponsorship in their blogs (Stichting Reclame Code, 2014). Bloggers are obliged to mention when one gets a monetary reward or any kind of other benefit (e.g. free products) from the sponsoring brand or company. The advent of these regulations has changed a lot for bloggers; the marketing and commercial intent of sponsored posts can no longer be hidden from their readers. Consequently, the attitude of readers towards sponsoring and sponsored posts is relevant when assessing the effectiveness and credibility of the advertisement and the blogger. Research concerning the credibility of blogs has been particularly focused on news, health, political, and medical blogs (Hansson, 2015; Metzger & Flanagin, 2008). However as mentioned, research about bloggers and the credibility of sponsored blog posts is limited. Colliander and Erlandsson (2015) examined the effects of acknowledging to readers that a company sponsored the blogger in exchange for favorable reviews of their products. The results showed that the attitude of the reader toward the blog and the credibility would suffer from this revelation, whereas, the attitude towards the sponsoring brand and the purchase intention would not decrease. However, the use of sponsored products was revealed by a third party after the respondents read the blog post and not by the blogger in the blogpost itself. Moreover, Lu, Chang and Chang (2014) concluded in their study that the sponsorship type, the type of reward the blogger received, has no significant effect on consumer attitude towards the post. The attitude of the reader remained unaffected regardless the type of benefit

10 THE STRENGTH OF SPONSORED BLOG POSTS the blogger received from the sponsor. A possible reason for this effect given by the researchers, may be that the honest reveal makes the readers feel the sponsored article is not trying to mislead or cheat them, and thus the received benefit by the blogger is no longer important. As stated, the provided compensation may take many forms, therefore, the study of Lu, Chang and Chang (2008) made use of two categories, direct-monetary (e.g. cash) and indirect-monetary (e.g. free samples) benefits. However, the researchers did not take into account the manner in which bloggers mentioned this received compensation in their blog post. Based on the earlier mentioned study conducted by Colliander and Erlandsson (2015) and Lu, Chang and Chang (2014) it is expected that the use of a sponsored blog post will lead to a lower purchase intention compared with a blog post where no sponsoring is used. As the mandatory disclosure of this relation between the blogger and the sponsoring company could decrease the credibility of the blogger and therefore, the purchase intentions of the reader. As mentioned, since blogger recommendation posts are a powerful marketing tool and useful in the consumer purchase decision processes, it is vital to understand how sponsoring and disclosure about the relation between the blogger and the sponsoring company, influences consumer’s purchase intentions (Lu, Chang & Chang, 2014). The mentioned studies show the effect of acknowledging the use of sponsored posts on readers, but it is not clear which effect the degree of disclosure has on the purchase intention of readers. Since it is obligated to disclose any form of sponsoring, the way in which bloggers mention this relation with the sponsoring company, might play a vital role. However, within the legal obligations bloggers are free to choose the form in which they disclose the sponsored relation. Therefore, it is interesting to investigate the possible effects of different degrees of disclosure. Consequently, this study tries to identify the effects of the obligatory disclosure on the purchase intention of consumers, by testing and comparing three degrees; complete disclosure, moderate disclosure and no use of sponsoring as the control group. Complete disclosure with regard to the sponsored relation consists of a textual explanation by the blogger wherein this relation is openly disclosed. Whereas moderate disclosure solely comprises of a minimal, but legally correct mention, in the form of a hashtag at the end of the blog post. As the earlier mentioned advertising code for social media states that the use of this simple hashtag (e.g. #spon, #paid or #adv) is sufficient to disclose the sponsoring of a product or service (Stichting Reclame Code, 2014). Both degrees of disclosure are legally correct but yet two extremes. Therefore, it is expected that full transparency of the sponsored relationship results in a higher purchase intention because

11 THE STRENGTH OF SPONSORED BLOG POSTS readers perceive this blogger as more credible. Conclusively, to test the potential impacts of the mentioned forms of disclosure, the following hypotheses have been stated;

H 1a: A sponsored blog post for a certain product or service will lead to a lower purchase intention than a blog post for a product or service that is not sponsored.

H 1b: Complete disclosure about the sponsoring of a blog post for a certain product or service will lead to a higher purchase intention compared with moderate disclosure.

Mediating role of source credibility on the relation between degree of disclosure and purchase intention Lu, Chang and Chang (2014) used the term source credibility as reference to whether an individual perceives an information source as unbiased, believable, true or factual. The source credibility theory claims that people are more likely to be persuaded by a source when it is presented as credible (Chu & Kamal, 2008). Positive characteristics of a message can increase the acceptance of readers by enhancing the perceived value of the source. However, if readers perceive a message as biased or used for other reasons than providing recommendations or experiences, the credibility of the source may be decreased and readers become insusceptible for the persuasive intent of the message (Lee & Koo, 2012). As mentioned, bloggers are obliged to disclose the connection between the sponsoring company and the sponsored blog posts, which in turn can influence the credibility of the blogger as perceived by the readers (Lee & Koo, 2012). However, the openness and public availability of the Internet makes it sometimes more difficult for readers to distinguish informational content from commercial content and reliable from unreliable sources (Metzger & Flanagin, 2008). The degree of disclosure could affect this distinction and thereby the perceived credibility of the blogger. The earlier mentioned study of Lu, Chang and Chang (2014) showed that if readers believe and perceive the shared content of a sponsored recommendation post to be true and have a positive attitude toward bloggers and their credibility, they will have a higher intention to purchase the recommended product in the particular blog post. It is assumable, that the extent to which the relationship between the blogger and the sponsoring brand is revealed affects the credibility of the blogger and thereby reader’s purchase intention. Thus, the credibility of the source, in this case the blogger, could mediate readers’ willingness to

12 THE STRENGTH OF SPONSORED BLOG POSTS purchase a product. It is expected that a blogger who uses a higher degree of disclosure is perceived as a more credible source which subsequently positively influences the purchase intention of the reader. Therefore, the following hypothesis will be tested:

H 2: Source credibility mediates the effect between degree of disclosure and purchase intention of the reader.

Blogger popularity The rapid expansion of the blogging phenomenon has caused a rapid increase in the number of bloggers. As earlier mentioned, the blogosphere consists of a small group of popular bloggers with millions of followers, who are able to make a living out of their blog. On the other hand, there is a large number of unknown, relatively unpopular bloggers with a small group of readers. The large group of non-influential blogs forms the long tail of the blogosphere and only a small group of popular and influential bloggers stand out (Agarwal, Liu, Tang & Yu, 2008). Trammel and Keshelashvili (2005) claim that popular bloggers are important influencers among their readers, because of their huge reach consisting of loyal visitors. Most studies that focus on the differences between bloggers split these groups on the basis of different types or features, for example, the comparison between celebrity bloggers, experts, and consumer bloggers as used by Chiu and Ho (2009). This classification based on expertise corresponds to the four types used by Freiden (1984). In addition, Wiener and Mowen (1986) stated that many studies use highly attractive sources versus highly negative sources. However, little research to date has focused on potential impacts that are caused by the difference in popularity of bloggers. Jin and Phua (2014) suppose that online popularity has a wide variety of connotations, for example the wide acceptance by peer group members or social dominance (Parkhurst & Hopmeyer, 1998). However, the number of friends or followers profile owners have on their websites or social networks is most frequently used as indicators of online popularity (Jin & Phua, 2014; Utz, 2010). In this study, popularity is being expressed as the number visitors a blog has, the number of comments and the number of likes a blog post received. It is likely that the popularity of a blogger contributes to the development of a certain expertise. In fact, Grossman et al. (2004) state that bloggers are self-proclaimed experts, as they often focus their blog on a specific topic or theme of interest. Agarwal et al. (2008) add to this idea that bloggers at large form their own special interest communities where they

13 THE STRENGTH OF SPONSORED BLOG POSTS share thoughts, opinions or ideas about this specific theme. Popular bloggers have presumably greater opportunities and more access to useful resources compared with smaller, relatively unpopular bloggers. Consequently, popular bloggers are more capable of making valid statements or provide accurate information. Therefore, it is expected that a more popular blogger has a more positive influence on purchase intention compared with a less popular blogger. These plausible differences between popular and unpopular bloggers could have an impact at the purchase decisions of their readers. Jin and Phua (2014) demonstrated in their study that the degree of popularity on the social networking site Twitter influences the perceived credibility of the source. The more popular the celebrity, the more he or she is perceived as credible. The researchers demonstrated that celebrities with a higher number of Twitter followers are perceived as higher in three dimensions of source credibility (physical attraction, trustworthiness and competence) than celebrities with a lower number of followers. Subsequently, a higher credibility causes a greater impact of the perceived persuasive intent (Lee & Koo, 2012). Although the experiment was conducted on the social network site Twitter, it indicates the influence of online popularity which may also be present for bloggers. However, due to the large number and diversity of bloggers, it is difficult for readers to make a distinction between credible and less credible sources (Lindquist, 2015). Elaborating on the literature as discussed above, it is expected that a higher perceived credibility of the source, in this case the blogger, causes a higher purchase intention of the reader. As research proves that the credibility of the information source, influences the persuasive impacts of blog posts and thereby the purchase intention of the reader. Therefore, the mentioned expectations have led to the following hypotheses;

H 3: A blog post about a certain product or service written by a popular blogger will lead to a higher purchase intention compared with a post from a unpopular blogger.

H 4: Source credibility mediates the effect between blogger popularity and purchase intention of the reader.

Finally, based on the discussed literature it is expected that the effect of disclosure differs for popular bloggers compared with unpopular bloggers. In other words, the more popular the blogger, the more depending he or she is on the degree of disclosure. Since popular bloggers are perceived as credible and important influencers, an honest revelation of

14 THE STRENGTH OF SPONSORED BLOG POSTS the sponsored relation might have a more positive influence on purchase intention compared with unpopular bloggers. The small group of popular bloggers rely more on sponsoring to maintain their blog and subsequently their income. Therefore, it might be case that there is more general acceptance for popular bloggers to be sponsored by large brands compared with relatively small and unpopular bloggers. Consequently, a honest explanation might allow a higher perceived credibility which in turn creates a higher purchase intention. So, this expected interaction has led to the following hypothesis;

H 5: The interaction between the popularity of a blogger and the degree of disclosure has a positive effect on purchase intention. Complete disclosure of the sponsored relationship will have a more positive influence on purchase intention for popular bloggers compared with unpopular bloggers

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Method

Experimental design The purpose of this study is to examine the influence of the degree of disclosure and popularity of the blogger on purchase intentions of blog post readers, whereby source credibility is taken into account as possible mediator. Participants are randomly assigned to one of six conditions in a 3 (degree of disclosure: moderate disclosure, complete disclosure, no sponsoring) x 2 (blogger popularity: popular blogger, unpopular blogger) between participants design. Thus, degree of disclosure and blogger popularity serve as the two manipulated variables and purchase intention as the dependent variable. Prior to the experiment a pre-test was conducted to design the stimulus materials and create six blog posts to measure readers purchase intention.

Materials To make the content of the stimulus materials interesting and appealing for both male and female participants, a neutral subject was chosen. The researcher made use of an experience service as it is expected that consumers mostly use subjective characteristics to evaluate these services (Zhu & Tan, 2007). This puts extra weight on the opinion of others, whereby blogs may be important influencers. Therefore, a review of a hotdog restaurant in Utrecht was used as content for the stimulus materials. For the used blog post, text and pictures of an existing post from the blog ‘Travellab.nl’ were used and thereafter adjusted for each condition. The manipulated text and corresponding pictures were presented in the layout of a fictional blog called ‘Reismee.nl’ to provide the participant with the look and feel of a real blog post. A fictional blog layout was used to eliminate the effects of potential recognition or foreknowledge from participants. Moreover, besides the stimulus material a survey was constructed to measure the dependent and mediating variables. The survey was designed with use of the online survey platform Qualtrics and consisted of eleven questions in total of which three questions concerning the demographic data of the participant. Subsequent to these three questions, participants were asked to read the following blogpost carefully and thereafter answer the asked questions. As mentioned, one of the six conditions and thus one of the six blogposts were randomly assigned to the participants, but the actual questions were equal across conditions.

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Manipulations of materials As mentioned, the used text was manipulated according to the aforementioned variables to create six experimental conditions. The first manipulated variable is the degree of disclosure. This variable was manipulated by the use of three different blog texts. Each of the texts contains one of the three forms of disclosure. In the control group, where no sponsoring was used, the blogger indicates that the reviewed restaurant has been visited because of her own interest. In the complete disclosure condition, the text contains an statement from the blogger stating that the restaurant sponsored the blog post and the blogger received a meal for free. For example, the sponsored relationship is expressed by the use of the following sentence; ‘This blog is written in association with Dogma’. Moreover, the header of the post contained the text “advertorial”. Lastly, the moderate disclosure condition contains no textual explanation about the sponsoring, but a brief mention in the form of a hashtag at the end of the post. The earlier mentioned advertising code for social media provides guidelines for the way in which the relationship between a blogger and the sponsoring company has to be disclosed. The use of hashtags (e.g. #spon, #paid or #adv) is sufficient to disclose the sponsoring of a product or service (Stichting Reclame Code, 2014). Therefore, the latter condition contains the mentioned hashtags to indicate the use of a sponsored blog post and no detailed explanation in the blog text itself. The differences between the degrees of disclosure in the sponsored conditions are very diverse and evident but nevertheless correct and sufficient according to the Dutch regulations. The second manipulated variable is blogger popularity. This manipulation was carried out by the use of several popularity cues in the blog post. For instance, the number of given comments, the number of page likes and social media likes. To test which cues were perceived by readers as indicators of popularity, a pre-test was conducted. In this pre-test (N = 36), participants were shown one popular and one unpopular post and thereafter asked to indicate the perceived differences between both posts. To check whether participants actually read the post, a control question concerning the content was added. Moreover, participants were asked to repeat the number of Facebook likes mentioned in the post. Lastly, participants were asked to indicate the cues that are most likely to indicate the popularity of a blogger. The results showed that participants indicate the number of visitors (M = 3.96, SD = 0.69), language usage (M = 3.96, SD = 1.04) and a professional layout (M = 3.96, SD = 1.04) as the most important cues. Shortly followed by the number of social media likes (M = 3.83, SD = 0.82), professional pictures (M = 3.67, SD = 0.82), and number of comments (M = 3.58, SD = 0.83). On the basis of these results, the number of visitors, likes and comments were used to

17 THE STRENGTH OF SPONSORED BLOG POSTS design the stimuli. As mentioned earlier, a professional lay-out, pictures and text were already being used to give to participant the experience of an actual blog. After the determination of the actual cues, the differences between popular and unpopular cues were defined on the basis of data from existing blogs. Five relatively popular and five unpopular bloggers were used to respectively count the number of given comments, number of likes and number of visitors for the first ten blog posts. The obtained average of these numbers served as the final implementation of the mentioned cues (i.e. 267 comments, 1367 likes, and 450,000 visitors in the popular condition and 6 comments, 7 likes, and the mention of a starting blog with few visitors in the unpopular condition). The texts in all six conditions were equal, apart from the manipulations as mentioned above. Moreover, all texts contained a positive sentiment, as it is unlikely that a sponsored post will be negative in nature and contain major criticism. The actual stimulus materials are added in appendix A.

Measurements The construct of the dependent variable purchase intention was measured with a scale developed by Putrevu and Lord (1994) and Taylor and Baker (1994), which is also used by Lu, Chang and Chang (2014) in their earlier mentioned study. Purchase intention was measured with four items. For example, one of the items contained of the following question; ‘I would consider visiting this restaurant’. Participants were asked to rate each item on a 5- point Likert scale from 1 (strongly disagree) to 5 (strongly agree). One item was reversed and recoded before analyzing the results. Moreover, the reliability of this scale proved to be satisfying, α = .77. The variable source credibility was measured using a scale developed by Ohanian (1991), as used by Pornpitakpan (2004) and Jin and Phua (2014). This construct was measured on the basis of the earlier mentioned key components trustworthiness and expertise. To measure trustworthiness, participants had to indicate the extent to which they perceived the blogger to be dependable, honest, reliable, sincere and trustworthy on a 5-point Likert scale from 1 (strongly disagree) to 5 (strongly agree). Moreover, expertise was measured according to the same principle with six items (i.e. expert, experienced, knowledgeable, qualified, skilled and informed). A factor analysis was conducted on the eleven items with orthogonal rotation. The results of the Kaiser-Meyer-Olkin measure confirmed the sampling adequacy for the analysis (KMO = .93) and all KMO values for inviduals items were greater then .91, which is well above the acceptable limit of .5 (Field, 2013). To obtain the eigenvalues for each factor, an initial analysis was run. The factor had an eigenvalue over

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Kaiser’s criterion of 1 and explained 59.66% of the variance. Thus, the eleven items could be retained in one factor. Moreover, apparent from the Chronbach’s alpha, the measured items have a high reliability (α = .93). On the basis of these results, the items were combined in the variable source credibility.

Participants and sample Because the purpose of this study is to examine blogs from a general perspective, the sample was gathered among both Dutch males and females. Participants were obtained with use of a convenience sample, participants have been collected through the researcher’s social networks (Facebook, Twitter and LinkedIn). A convenience sample has the advantage that data can be gathered in a quick and inexpensive way, without complicating and time- consuming selection processes. On the other hand, selection errors could cause potential biases of the final results. However, the limited time period of this research causes a convenience sample to be the most appropriate sample. In total, 342 participants participated in the study, of which 235 participants are used in the analysis (N = 235). Firstly, 88 participants were deleted from the sample because they did not complete the survey. This resulted in a drop-out rate of 25.7 percent. Moreover, two participants were deleted as their answer was ’yes’ to the control question ‘Are you familiar with the blogger?’ As stated earlier, the blog post was presented in a fictional lay-out with a fictional blogger and blog name. Therefore, it can be assumed that these participants have not completed the questionnaire with precision, which in turn might bias the results. Lastly, 17 participants were deleted because they were minors. The final sample consisted of 168 women (71.5 %) and 67 men (28.5 %), the distribution of gender is not equal. However, this does not cause any problems concerning the validity of this research as blogs are predominantly read by females. With regard to age, the sample is not an optimal reflection of the blog reading population as the participants have a relatively high average age of 30.73 (SD = 11.95). Moreover, the sample contains an accurate reflection of different educational levels as 28.5 percent of the participants is low-skilled (secondary vocational education) and 46.0 percent highly educated (26.0 percent higher professional education and 20.0 percent university degree). Lastly, participants read on average once a week one or more blogs.

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Procedure The researcher posted an electronic survey through the online survey platform Qualtrics and distributed the link via social media (Facebook, Twitter and LinkedIn) in order to obtain a convenience sample through a snowball effect. After clicking on this link, participants were randomly assigned to one of six mentioned conditions. The first questions were focused on the demographic data of the participant, such as age and gender. Subsequently, the participant was asked to indicate how frequently they read blogs. Thereafter, participants were instructed to read and observe the following blog post closely. One of six of the manipulated posts was then shown to the participant, which had to be viewed for at least fifteen seconds before the participant could proceed to the following page. After reading the blog post, participants were asked to answer questions measuring the dependent and control variables. Then the manipulation checks followed and thereafter the participant was thanked for his participation. Participants could open the link on both smartphones and laptops. When the questionnaire was prematurely terminated and the participant drop-out, it could be opened on a later moment and still be completed. The complete questionnaire is added in appendix B.

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Results

The used statistical test are chosen on the basis of the characteristics of the dependent and independent variables. Hypothesis 1A, 1B, 3 and 5 are tested with use of a factorial Anova. Moreover, hypothesis 2 and 4 are tested with use of a mediation analysis. For the execution of this analysis the SPSS macro ‘PROCESS’ (Hayes, 2013) was used. The data was checked on several assumptions before performing the various analyses. In the following chapter, the analysis are discussed and the various hypotheses are examined one by one.

Manipulation check Besides the control questions, a manipulation check was added to control whether the mentioned manipulations were successful. Firstly, with use of two questions participants were asked to indicate on a 5-point Likert scale if they perceived the blogger to be popular or not. The reliability of these questions proved to be satisfying (α = .77) and were therefore recoded into one single variable. After that, the manipulation appeared to be successful, t (233) = 2.55, p = .011. Participants in the popular condition perceived the blogger to be more popular (M = 3.06, SD = 0.68) compared with participants in the unpopular condition (M = 2.86, SD = 0.55). The second manipulation check consisted of one question with on 5-point Likert scale from 1 (strongly disagree) to 5 (strongly agree), which measured if participants perceived the post as sponsored or not. The overall Anova was not significant (F(2,232) = 2.19, p = .115). However, when the sponsored conditions are compared with the control condition, the manipulation seemed to be successful. As the contrast analysis indicates significant differences between the means of the two sponsored conditions and the condition without sponsoring, t (232) = 2.08, p = .038, r = .14. Participants in the complete disclosure condition (M = 3.42, SD = 0.94) and the moderate disclosure condition (M = 3.40, SD = 0.89) considered the blog fairly even to be sponsored, compared with the control group (M = 3.15, SD = 0.90).

Effect of degree of disclosure on purchase intention As stated, to test the effects of degree of disclosure on purchase intention, a factorial Anova was performed. The scores of both variables degree of disclosure and popularity were not normally distributed, as indicated by the Kolmogorov-Smirnov test (Ddegree of disclosure (253)

= 0.23, p < .001 and Dpopularity (253) = 0.34, p < .001). Due to not normally distributed data,

21 THE STRENGTH OF SPONSORED BLOG POSTS the p-value might be biased and not completely reliable. There were no significant differences in the variances of the groups, as indicated by the Levene’s test (F(5,229) = 0.58, p = .716), so the assumption of homogeneity of variance is met. Participants in the moderate disclosure condition have on average a score of 3.28 (SD = 0.71) on purchase intention, closely followed by participants in the control group without any form of sponsoring (M = 3.26, SD = 0.66) and finally the participants in the complete disclosure condition (M = 3.03, SD = 0.76). The Anova showed a significant main effect of degree of disclosure on purchase intention, F(2,229) = 3.30, p = .039, 휔2 = 0.02. However, the Helmert contrast analysis showed that participants in the sponsored conditions did not significantly differ from participants in the condition without sponsoring (p = .259). Thus, hypothesis 1A is not supported as the use of sponsored blog posts does not lead to a more negative purchase intention compared with no use of sponsoring. Within the sponsored conditions, moderate disclosure leads to a higher purchase intention compared with complete disclosure, which is confirmed by the contrast analysis (p = .023). Therefore, hypothesis 1B is also not supported as, in contrast with the expectation, moderate disclosure leads to a more positive purchase intention.

Mediating effect of source credibility on disclosure and purchase intention To examine whether the perceived credibility of the source mediates the relationship between the degree of disclosure and purchase intention, a mediation analysis was conducted using Hayes’(2013) PROCESS macro for SPSS (Model 4). This analysis was performed according to the recommendations of Preacher and Hayes, with 5000 bootstrapping samples and 95% bias-corrected and accelerated confidence intervals to evaluate indirect effects. Mediation was considered to occur if zero was not included in the 95% confidence interval. First, the effect of degree of disclosure on source credibility was explored with use of an Anova. No main effect of degree of disclosure on source credibility was found as indicated by the Anova (F(2,232) = 1.49, p = .228). Participants in the complete disclosure condition obtained an average score of 3.23 (SD = 0.71) on source credibility. Moreover, the moderate disclosure condition obtained an average score of 3.35 (SD = 0.59) and participants in the control group without any form of sponsoring obtained an average score of 3.41 (SD = 0.66). Furthermore, the mediation analysis revealed a significant total effect of degree of disclosure on purchase intention (b = 0.12, t = 2.06, p = .041). However, the direct effect of disclosure on purchase intention appeared not to be significant, b = 0.07, t = 1.41, p = .161.

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Also the indirect effect seemed not to be significant as the confidence intervals crossed zero, b = 0.04, Bca CI [-0.008, 0.170]. Therefore, hypothesis 2 is not supported as source credibility does not mediate the relationship between the degree of disclosure and purchase intention. See Figure 1 for the complete mediation model.

Source credibility

b = 0.09, p = .091 b = 0.53, p < .001

Degree of disclosure Purchase intention

Direct effect, b = 0.07, p = .161 Indirect effect, b = 0.04, Bca CI [-0.008, 0.170] Figure 1. Model of degree of disclosure as predictor of purchase intention. The confidence interval is a 95 percentile CI based on 5000 samples.

Effect of popularity on purchase intention The purchase intention of participants who read the blog written by a relatively unpopular blogger is slightly higher (M = 3.27, SD = 0.71) compared with readers of the popular blogger (M = 3.11, SD = 0.73). This little difference is in contrast to the expectation that popular bloggers have a more positive influence on purchase intention than unpopular bloggers. As mentioned, the scores of the variable popularity were not normally distributed

(Dpopularity (253) = 0.34, p < .001), therefore the p-value might not be completely reliable. In addition, the assumption of homogeneity of variances is met as the Levene’s test is not significant (F(5,229) = 0.58, p = .716). However, the factorial Anova showed no significant main effect of popularity on purchase intention F(1,229) = 3.20, p = .075, 휔2 = 0.001. Thus, hypothesis 3 is not supported. Popular bloggers seem not to have a more positive influence on purchase intention compared with unpopular bloggers.

Mediating effect of source credibility on popularity and purchase intention To examine whether the perceived credibility of the source mediates the relationship between the popularity of the blogger and purchase intention, another mediation analysis was conducted. This analysis was based on the same principles as used with the previous mediation model. The results revealed a significant indirect effect of popularity on purchase

23 THE STRENGTH OF SPONSORED BLOG POSTS intention through source credibility, b = 0.64, Bca CI [0.770, 0.442]. As the 95% bootstrap confidence intervals do not include zero, significance can be assumed. This represents a relatively small effect, K² = 0.072, 95% BCa CI [.012, .133]. The model explains 23.9% of the variance in purchase intention. Thus, the credibility of the source mediates the relationship between the popularity of the blogger and purchase intention of the reader. Therefore, hypothesis 4 is supported. Figure 2 displays the complete mediational model.

Source credibility

b = 0.18, p = .033 b = 0.53, p < .001

Popularity Purchase intention

Direct effect, b = 0.06, p = .442 Indirect effect, b = 0.096, Bca CI [0.016, 0.248] Figure 2. Model of popularity as predictor of purchase intention. The confidence interval is a 95 percentile CI based on 5000 samples.

Interaction effect of popularity and degree of disclosure on purchase intention The results of the earlier mentioned factorial Anova can be used to test the interaction between the popularity of the blogger with the degree of disclosure. As stated, both variables were not normally distributed, therefore, the p-value might be biased and should be interpreted with caution. A significant main effect was found for the degree of disclosure (F(2,229) = 3.30, p = .039). However, no significant main effect was found for the popularity of the blogger, as indicated by the results F(1,229) = 3.20, p = .075. Thus, the popular condition (M = 3.11, SD = 0.73) did not significantly differ from the unpopular condition (M = 3.27, SD = 0.71). Additionally, no significant interaction effect was found between both variables, F(2,229) = 0.60, p = .552. This indicates that the effect of the disclosure degree was not depending on the popularity of the blogger. Thus, hypothesis 5 is also not supported as there is no interaction between popularity and degree of disclosure. As can be seen in Table 1 , all the means are in the opposite direction as expected. However, the differences are very small and cannot be generalized to the population.

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Table 1. The means and standard deviations (between round brackets) of the variable ‘purchase intention’. ‘n’ represents the number of respondents.

Degree of disclosure Popular (n = Unpopular(n = Total (n = 119) 116) 235)

Complete disclosure (n = 83) 2.89 (0.75) 3.16 (7.62) 3.03 (0.76)

Moderate disclosure (n = 77) 3.27 (0.71) 3.30 (0.73) 3.28 (0.71)

No sponsoring (n = 75) 3.16 (0.69) 3.37 (0.61) 3.26 (0.66)

Total 3.11 (0.73) 3.27 (0.71)

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Conclusion and discussion

This study tried to examine the influence of blogger popularity and the degree of disclosure on purchase intention of the reader. Moreover, credibility of the source was taken into account as a possible mediator. Based on the conducted research, the research question ‘Which effects have the popularity of a blogger and the degree of disclosure about the use of sponsored blog posts, on the purchase intention of blog readers?’ can be answered as follows: purchase intention of blog readers do not appear to be influenced by the popularity of the blogger. However, the extent to which bloggers reveal the sponsored relationship and the credibility of the concerning blogger seem to have an effect on the readers’ purchase intention. The results are below discussed in more detail. Despite disappointing results, this study makes several theoretical contributions to the field of online marketing and advertising. As mentioned, previous conducted research evaluating sponsored blog posts is limited. Therefore, this study aimed to better understand the deployment of sponsored blog posts and add quantitative experimental research to the existing literature. Moreover, the inconsistencies with previous literature underline that more research is needed.

Sponsored blog posts The first three hypotheses in this study sought to determine the effects of the extent to which bloggers reveal their sponsored relationship with a certain brand, defined in this study as the degree of disclosure. As expected, the degree of disclosure appears to affect the purchase intention of blog readers. However, there is no significant difference in purchase intention of blog readers when using sponsored post compared with unsponsored posts. These findings are in line with the earlier mentioned results of Colliander and Erlandsson (2015), who concluded that purchase intention did not decrease after revealing the sponsoring of the blog post. It was expected that a honest and comprehensive reveal of the sponsored relationship would lead to a higher purchase intention, as substantiated by Lu, Chang and Chang (2014). In contrast to this expectation, we found that a minimal but legally correct mention of the sponsored relation ensures a relatively higher purchase intention compared with a honest reveal. Therefore, complete disclosure does not necessarily have to be better or more appreciated. However, these results must be interpreted with caution because of the potential bias in the results due to the partially successful manipulation. Since the participants did not perceive the differences between the complete and moderate sponsored conditions.

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The exact explanation for this notable and surprising result it not fully understood. These findings can not be explained by the fact that readers did not notice the inconspicuous indications (in this case the hashtags) in the moderate disclosure condition. Because there was a difference in the manipulation check score between participants in the moderate disclosure condition and the control condition. So participants did notice a difference. However, a possible but arguable explanation might be that participants perceived the clearly present indications in the complete disclosure condition as disturbing and distracting and thus scored lower on purchase intention. But no clear reason can be identified to explain the unexpected results. A possible explanation for the failure of the manipulation check is the fact that the relatively large group of older participants, which caused a high average age, were dealing with nescience or inexperience with blogs. Which in turn caused readers to miss or not comprehend the indications of a sponsored blog post. Moreover, participants were forced to read the blogpost in an artificial setting. Normally, participants would read blogs out of personal interest or under different conditions. Therefore, the results might not completely match a realistic and normal situation. In addition, it is somewhat surprising that despite the strong theoretical foundation, the credibility of the source, in this case the blogger, could not explain the mentioned relation. A higher degree of disclosure does not cause a higher perceived source credibility. The findings of the current study do not support previous research, as the results are not in line with the study of Lu, Chang and Chang (2014). These researchers showed that if readers perceived the content of a sponsored recommendation post to be true and have a positive attitude toward the blogger and its credibility, they will have a higher intention to purchase the recommended product in the particular blog post. However, the mentioned research measured the attitude and trust of participants towards sponsored recommendation posts and did not use different types of disclosure as a variable. Because the findings of this study are unexpectedly in contrast with previous studies, it might raise questions regarding the actual role of source credibility. Since limited research has been conducted on sponsored blog posts, this research could serve as a base for future studies. There is abundant room for further progress in determining the effects and use of sponsored blog posts. For example, further experimental investigations are required to determine how readers perceive the actual indications in the text. Are the used indications sufficient and are they perceived correctly, or do they evoke

27 THE STRENGTH OF SPONSORED BLOG POSTS irritation among readers? Moreover, it is not clear if readers understood the hashtags as used in the moderate disclosure condition. In addition, since source credibility failed to explain the effect of degree of disclosure on purchase intention, other processes should be examined to explain this relation. For instance, the attitude of readers towards the blogger or blogs in general as used by Lu, Chang and Chang (2014). Or the role of para-social interaction as Colliander and Erlandsson (2015) already proved that a lower credibility and attitude toward a sponsored blog can be partially explained by para-social interaction.

Blogger popularity As mentioned in the literature review, this study also tried to evaluate the importance and influence of blogger popularity. Contrary to the expectations, the popularity of the blogger did not have any effect on purchase intention of blog readers. Based on the research by Jin and Phua (2014), it was expected that a more popular blogger would induce a higher purchase intention. This study has been unable to demonstrate the previously proven influence of popularity. On the other hand, this study has confirmed the findings of Jin and Phua (2014) which found that the degree of popularity on the social networking site Twitter influences the perceived credibility of the source. The more popular the source, the more he or she is perceived as credible. Subsequently, the more credible the source the higher the purchase inention of the reader. Therefore, the results of this study complement this idea since source credibility proved to be a mediating variable. The relevance of a blogger being credible is clearly supported by the current and earlier mentioned findings. These results are consistent with the idea of Trammel and Keshelashvili (2005) who stated that popular bloggers are important influencers among readers, with a high perceived credibility. The findings of the current study suggest that popularity does not directly influence purchase intentions of readers. Therefore, more extensive research is required to investigate why popular bloggers are perceived as more credible compared with unpopular bloggers. And which factors cause readers to judge popular bloggers differently than unpopular bloggers. In addition, the use of fictive bloggers limited this study. The current experiment only made use of popularity cues in the form of numeric indications. However, results might be stronger when using real and existing bloggers, who are actually popular and well known. These popular bloggers might evoke stronger feelings or emotions among readers, which

28 THE STRENGTH OF SPONSORED BLOG POSTS result in a more realistic effect. Therefore, further experimental investigations are needed to establish the actual effects of these bloggers.

Research limitations Although this research has yielded notable and unexpected results, improvements can be made in the design and execution of the experiment. To begin with, the generalizability of this research is subject to certain limitations because the experimental sample was obtained with use of convenience sampling through social media. The sample consisted mainly of females, nevertheless, this poses no problems concerning the validity of the research since most blog readers are female. However, the sample is not a true reflection of the complete Dutch population. Moreover, the convenience sample ensured a relatively high average age with a large standard deviation. Making the experimental sample not completely match the average blog reader. This fact was confirmed by the extent to which the sample reads blogs, only once a week. This could have caused the sample to be inexperienced with blogs, which in turn biased the results. Therefore, the results can not be generalized to the complete Dutch population. The external validity could be improved by making use of a random sample to select the participants. Second, the manipulation of the degree of disclosure has not been completely successful as indicated by the conducted Anova. Therefore, the results of this study concerning this variable should be interpreted cautiously. In addition, the choice for a particular product or service, in this case a review of a hotdog restaurant, could have reduced the validity. Because, when the participants already have a certain attitude concerning this service or product, results will be different compared with participants who are not familiar with the product or service. Therefore, it is recommended for future research to use multiple blogs in the experiment, containing different topics to exclude coincidences and improve reliability of the results. Finally, participants were specifically asked to read the blog careful and attentively. However, this way of reading does not completely correspond with the way a person reads for his own enjoyment or personal motivations. The substantive information in the blog post is properly recorded by this careful reading, but the peripheral information which is used to make quick decisions might be missed. However, the ability to create a realistic environment and circumstances is subjected to certain limitations as the data was gathered in a experimental situation. Therefore, it should no noted that the results of this experimental situation may not fully correspond to reality.

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Managerial and scientific implications Despite disappointing results, the findings of this study offer valuable insights for both bloggers and sponsoring brands or companies. More in-depth knowledge on the use of sponsored blog posts and the effects of blogger popularity would help sponsoring brands to better understand this form of advertising and improved deployment. Since bloggers are obliged to mention any form of sponsorship on their blogs, the commercial intent of sponsored posts can no longer be hidden for readers. Therefore, knowledge about the use of such posts and the attitude of their readers is vital for bloggers when assessing effectiveness. The purpose of the current study was to identify the influence of degree of disclosure and popularity of the blogger on consumer’s purchase intention. The results demonstrate that a mandatory indication of the sponsored relation does not have to be comprehensive to gain the trust of readers. In contrast, a minimal mention provides a higher purchase intention compared with a comprehensive explanation. Depending on the purpose of a message, this impact is something to keep in mind when writing and publishing sponsored blogs. Moreover, purchase intention of the blog readers is not influenced by the popularity of the blogger. Taken together, these results suggest that the use of sponsored blog posts is not fully understood yet. The findings do not complement those of previous research which indicates the need for further research.

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Appendix A

Stimulus material condition 1 – popular blogger & complete disclosure

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Stimulus material condition 2 – unpopular blogger & complete disclosure

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Stimulus material condition 3 – popular blogger & moderate disclosure

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Stimulus material condition 4 – unpopular blogger & moderate disclosure

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Stimulus material condition 5 – popular blogger & no sponsoring

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Stimulus material condition 6 – unpopular blogger & no sponsoring

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Appendix B

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