Analysis of Twitter Messages About the Osaka Metropolis Plan in Japan
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2017 IEEE International Conference on Big Data (BIGDATA) Analysis of Twitter Messages about the Osaka Metropolis Plan in Japan Kouki Hayashi Eiichi Umehara Ota Ward Office dept. of Information Systems Tokyo, Japan Tokyo City University e-mail: [email protected] Yokohama, Japan e-mail: [email protected] Yuuki Ogawa Ritsumeikan University Shiga, Japan e-mail: [email protected] Abstract—This study focused on Twitter, which is expected to become an increasingly influential tool of political II. PREVIOUS RESEARCH communication, and sought to validate public opinion formation process theories such as the concentration of A. Verification of the spiral of silence on Twitter opinions and announcement effects. We analyzed tweets about Noelle-Neumann[3] proposed the hypothesis that people the Osaka Metropolis Plan, which was the subject of a desire to avoid isolation from others, and when they feel that referendum in May 2015. We classified tweets and accounts their opinion is in a minority in society with respect to a based on support for or opposition to the plan, using a natural certain issue, they refrain from expressing it in public. language process and latent Dirichlet allocation, and by Ogawa et al.[5] analyzed a social survey and action logs to comparison with newspaper articles. We analyzed changes in the number of posts and active accounts based on the results. investigate whether the number of messages posted on We found that the spiral of silence theory did not apply. We Twitter affects majority cognition and homogeneity of also investigated retweet networks using social network opinion in surrounding personal networks. They asked the analysis, and found that support and opposition were clearly subjects about their agreement with/opposition to nuclear divided in a network structure. Moreover, we found several power plants, the importance of this issue, their amount of accounts with extremely high degree centrality and knowledge, interest in politics and their prediction of the betweenness centrality, thereby indicating possible validation majority. They subsequently analyzed tweet data, and found of an opinion leader effect and the announcement effect. that people do not recognize themselves as being in the majority, even when many of their friends have the same Keywords—Osaka Metropolis Plan; Twitter; Announcement opinion. This result suggests that even though Twitter users effect, Limited effect theory have the same opinion as others around them, they may not recognize that they are in the majority on Twitter. On the I. INTRODUCTION other hand, recognition that their own opinion is in the majority had a positive effect on the number of messages Japan approved the Internet for use in the election posted on Twitter. This result may support the notion of a campaign of 2013, making it likely that the Internet would be spiral of silence. increasingly used for communication in elections. Using a panel survey, Hashimoto et al. [8] examined how the Internet B. Limited effect model affected House of Representatives elections in Japan. They Unlike powerful effect models such as the spiral of found that 40.2% of people reported seeing election-related silence, the limited effect model states that the effects of information on the Internet in the run-up to the election. mass media are limited. Lazarsfeld[2] examined seven panel However, there is no conclusion as to whether the surveys in Erie County, Ohio, during the 1940 US Internet is a useful medium for political communication, and presidential election over six months. The effect of each there is controversy over its use. Therefore, this study party’s campaign through media such as newspapers, considers whether public opinion formation theories remain magazines, or radio on voting behavior was one of valid. We focus on Twitter, and analyze the Osaka reinforcement. Metropolis Plan on which a referendum was held in Osaka Voters exposed to many campaigns in the media may City on May 17, 2015. This proposal was the most important have already decided who to vote for and may have great policy of the Osaka Ishin Association (One Osaka) local interest in the elections. On the other hand, voters who are political party. In the referendum, there were 694,844 votes not interested in politics may change their attitudes and in favor and 705,585 votes against. The proposal was thus behaviors because of “opinion leaders” who advise or defeated because the opposition won by a small margin. persuade people around them during the election period. Klapper[1] attempted to generalize a campaign effect and noted that the main effect of the mass media is the reinforcement of existing attitudes, so that people with a 978-1-5386-2715-0/17/$31.00 ©2017 IEEE 2982 similar opinion tend to gather around specific individuals 28,417 tweets (31.5%), 1,196 replies (1.3%), and 60,677 who maintain that opinion. retweets (67.2%). C. Opinion leaders on Twitter The number of tweets increased as the referendum date approached. There were 21,699 (24%) tweets on the 17th Yamamoto et al.[9] examined the features of opinion day of the referendum campaign. This was 814% of the leaders and their roles on Twitter. They categorized opinion 2,666 tweets recorded on May 4, the first day of our analysis. leaders as specialists who are the starting point for There were 7,771 tweets on the 16th day of the referendum, information and act as information intermediaries, and they and the number increased by 64.2% by May 17. analyzed social surveys and Twitter logs. They asked their respondents to answer questions concerning their opinions IV. CLASSIFICATION OF SUPPORT/OPPOSE TWEETS and knowledge of nuclear power plants, recognition of the importance of the issue, anxiety about nuclear power plants, A. Classification of issues using topic analysis and homogeneity of friends or followers, and analyzed tweet data. They found a correlation between the number of To identify Twitter discussions on the Osaka Metropolis messages posted by specialists with expert knowledge who Plan, we analyzed tweets using topic analysis, which is a tool were deeply involved in this field and the number of their that classifies content mechanically into topics using natural followers and friends. However, there was no correlation language processing. First, we divided the collected Japanese between being an intermediary, a center of communication tweets according to words using a morphological analysis and playing the role of information mediation, and the program (IGO) by 1gram. Then we classified the tweets into number of followers and friends. Their results indicate that in 10 topics using latent Dirichlet allocation. From this an environment such as Twitter, where people can easily extraction, words such as “referendum,” “approval,” and communicate directly with others, people tend to “oppose” were conspicuous. In addition, tweets contained communicate directly with trusted specialists. the names of people who had clearly indicated approval or disapproval, such as representative Toru Hashimoto (Osaka D. Announcement effect Ishin Association), Secretary General Ichiro Matsui (Osaka Urashima et al.[4] noted that the announcement effect Ishin Association), Chief Cabinet Secretary Yoshihide Suga, refers to the effect that election predictions based on public and Professor Satoshi Fujii. opinion polls in the media have on voting behavior. In a B. Main issues in the Osaka Metropolis Plan review of work on the announcement effect, Kamegaya (2001) highlighted the following findings. Based on the results of the topic analysis and news Lazarsfeld[2] studied voting behavior and found a stories in four major Japanese newspapers (Yomiuri Shimbun, positive correlation between opinion polls and votes for Asahi Shimbun, Sankei Shimbun, and Mainichi Shimbun), we candidates. He claimed that the reason for this is that the identified the main issues of contention between proponents candidates (bandwagons) who are regarded as having an and opponents of the Osaka Metropolis Plan on Twitter. advantage in polls tend to receive votes. Klapper[1] pointed Supporters of the reform of the Osaka governance system out that public opinion polls also affect minority opinions, so believed that the current Osaka City administrators were very public opinion does not change only in the direction of the poor in terms of fiscal and administrative efficiency. They majority. This is a phenomenon whereby votes are gained by insisted on reforms to reduce the number of representatives candidates likely to be defeated, contrary to the bandwagon who allegedly liked to line their own pockets because of effect, which is known as the underdog effect. Ceci and vested interests, and to reform the redundant and inefficient Kain[6] confirmed an apparent underdog effect in a 1970s administration of Osaka Prefecture and the Osaka City British election. Shiratori [7] examined the reverse of the government. They often referred to the speeches of well- bandwagon effect and the underdog effect. They found a known public figures (such as Yoshihide Suga, Yoichi withdrawal effect, whereby the winning candidate’s votes Takahashi, and Jiro Shiboh) who expressed approval of the are reduced, and a fleeing effect, whereby the losing plan and opponents tended to evaluate them highly. candidate’s votes are reduced. With the withdrawal effect, Conversely, they strongly criticized the Osaka Liberal confidence that a candidate can win will cause supporters to Democratic Party, the Democratic Party, the Komeito Clean be complacent and lethargic. In the fleeing effect, if Government Party, and the Japanese Communist Party, supporters are convinced that a candidate will be defeated, which opposed the plan. They criticized that their opponents they avoid voting. did not have a growth strategy to replace the Plan, and rejected opponents’ claims as false rumor III. DATA Opponents of the plan were very skeptical of Toru Hashimoto, the representative of the Osaka Ishin Association, We collected tweets concerning the Osaka Metropolis and frequently cited Hashimoto’s previous speeches.