Changing Patterns of Recreation over Time: What Can Be Learned from Panel Studies?

Thomas A. Heberlein Department of Rural Sociology University of -Madison-USA

Walter F. Kuentzel School of Natural Resources University of Vermont-USA

Rebecca A. Grossberg Department of Rural Sociology University of Wisconsin-Madison-USA

                    

Please Do Not Cite without Permission Updated Versions at http://nature.snr.uvm.edu/ai/ Introduction Final June 28, 1999

The title of this paper is misleading. It suggests a dry dusty methodological treatise on the virtues of using panel data. Usually in these papers the authors have no real data but give clear examples of what might be learned IF time series or panel data were available. Because it takes a long time commitment, substantial and sustained resources, institutional stability, and a dose of good luck to collect data on individuals over time there are many more what if papers than what is papers. This paper, which began 24 years ago in a small National Park in the United States is the real thing. Today we will be reporting the first glimpses of what one can see with longitudinal data from three cross-sectional surveys, a three-wave panel and a two-wave panel of visitors to a North American National Park. We surveyed visitors to the National Lakeshore in 1975, 1985, and 1997. We also surveyed the 1975 visitors 10 years and 22 years after they were first surveyed, and surveyed the 1985 visitors 12 years after they were first sampled.

A true understanding of growth and change requires time-series data. As Stynes and Driver (1990) note, "the research questions raised by the leisure benefits area dictated methods that many leisure scientists were not very experienced with, such as, experimental and longitudinal designs." There have been repeated calls from public sector managers and private sector industry officials for trend data on recreation participation. The growth of outdoor recreation in the 1970s along with growth in domestic and international tourism in the 1980s has created a need for a historical perspective that projects the future of recreation and leisure from an understanding of the past. In response, researchers have sponsored four Trends Conferences in Outdoor Recreation between 1980 and 1995. More than 100 papers were presented at the 1990 conference, but only a handful presented findings from time-series data. The use of time-series data increased somewhat in the 1995 conference, although most of these studies relied on multiple cross-section designs. Overall, little panel data exists in the recreation research field, and even fewer panels extend beyond five years.

Many researchers have lamented the lack of longitudinal data. Louviere and Timmermans' (1990) review of the recreation choice literature asserts that "all of the preceding types of models historically have been strictly cross-sectional: preferences or choices are observed and modeled at a single point in time. Unfortunately, such data may not be sufficiently rich to distinguish and estimate the effects of the many sources of influence on choice behavior. Consequently, interest in longitudinal or panel data has increased considerably and models of dynamic choice behavior have been proposed." Similarly, Hellerstein and Mendelsohn review research on the economic impacts of travel and note that "...knowledge could be gained by going beyond this 'single snapshot' of the world, by augmenting the experiment with multiple samples. One obvious source for different samples is in the time dimension -- with different samples gathered at different points in time. While exceptions exist (e.g., Peterson & Stynes, 1985), the potential of multi-year data has not been exploited by travel cost modelers." What little panel data exists in the recreation literature tends to utilize a pretest/post-test design. These studies tend to cover a period spanning a few months, and seldom cover more than five years at a time.

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Design of the Apostle Islands Study

In 1970 the US Congress designated 20 Islands in on the North coast of Wisconsin as the Apostle Islands National Lakeshore. This resource was to be managed by the National Park Service as a National Recreation Area. For the most part, National Lakeshores are like National Parks except that they are open to more diverse recreation (like hunting) than other national parks. . The park began acquiring property from the state and private individuals in 1971, and had their first operational budget of $68,000 in 1972. In 1975 the senior author along with graduate assistant Jerry Vaske designed a visitor survey of those who boated to, camped on, or visited the Islands. The explicit goal of this study was to follow up both the 1975 visitors over time to see how they reacted as the new park developed. We were explicitly interested in crowding and visitor displacement. Would the development of the Park crowd out the current visitors and would they be replaced by a new set of less sensitive visitors? This research was funded by the UW-College of Agriculture Experiment Station. The new unit in the Park Service was struggling to become operational and were hard pressed to study potential future problems.

The 1975 study used various listing procedures (Heberlein and Vaske, 1979) to locate and census boaters, campers, and day visitors during that summer. After the season those who filled out census cards were sent a mailed questionnaire asking them to describe their activities, their activities on a best trip and their expectations, perceptions, and satisfactions. This was the first cross section. Completed questionnaires were returned from 649 of the boaters (74% response). This became the first (1975) cross-section survey of Apostle Island visitors.

In 1985 the number of boater camper nights (the NPS estimate of the number of people who moored or docked their boat at one of the islands over night) had increased from 7117 in 1976 to 15,828 in 1985. The other two groups, campers and day visitors, had remained about stable. Consequently the 1985 survey was focused only on the boating group. The survey was funded by the Wisconsin Sea Grant Institute. This time we stationed samplers on islands at randomly selected times throughout the boating season. In the evening, these samplers would approach all anchored or docked boats who were staying the night, and collect names and addresses of all passengers over 16 on each boat. At the end of the season, a sample of these boaters were sent mailed surveys. The sample was stratified by the island where individuals were registered, and was proportionate to total overnight use at each island and by peak season and shoulder seasons at the Park. Because people who boat more days are more likely to fall in the sample, the final data were inversely weighted by boater days. 500 questionnaires were mailed to boaters and 377 were returned for a response rate of 75.4 %. This became the second (1985) cross-section. In addition 500 of the 648 respondents from 1975 were relocated and mailed a survey to determine what they had been doing since 1975. Of the 500 people located, 397 returned questionnaires in 1985 (79.4%) , so we have a 1975-85 panel surveys of the same

Page -3- Final June 28, 1999 people at two points in time. Trudy McKinnel and Laurie Erwin were research assistants on this project.

In 1997 Walt Kuentzel, who had done his dissertation on the Apostle Islands data, and was an Assistant Professor at the University of Vermont was a co-principal investigator and supervised the field work and constructed the surveys. The same sampling methodology employed in 1985 was used again in 1997. Interviewers were stationed on specific islands to approach all boats anchored or docked overnight to register all visitors over 16 years old. A sub sample of these registered boaters were then selected to receive a follow-up questionnaire. Again, the selection process was proportionately stratified by total overnight use at each island and by seasonal use at the Islands.

Rebecca Grossberg at the University of Wisconsin supervised the 1997 survey administration. A 32 page questionnaire was sent to 562 people registered in 1997 and 389 were returned for a 69.2% percent response rate. These responses comprised the third (1997) cross- section survey. In addition, 409 of the 649 respondents in 1975 were located and mailed surveys. Of these 249 were returned for a 60.9% response rate. This produced the third wave of the 1975- 1997 panel. Next, 327 of the 377 respondents in 1985 were located and mailed surveys. Among these groups 160 were returned for 48.9% response rate. This produced the second wave of a 1985-1997 panel. Finally, there was a new group of boaters visiting the islands in 1997 sea kayakers. A special survey was sent to 191 overnight sea-kayakers we registered during 1997. Of these, 103 surveys were returned for a 53.9% response rate.

For a detailed discussion of the 1997 methodology see Appendix 1

Results and Discussion

Multiple time series studies and panel studies provide at least three types of information that are distinct from the information provided by a single cross-sectional or qualitative case study. First are the major unobserved changes that catch people off guard, and that may be a driving force behind the social system. Change is obviously unavailable in single cross-sectional studies except as individuals use retrospective reflections to assess change. Longitudinal data allows one to monitor structural changes that may escape individual scrutiny. Second, there are things that remain remarkably constant over time in spite of dramatically different and changing populations. Finally are the things that simply require time for processes to unfold. Without continued monitoring, one can not assess the emergent characteristics of these social processes. We will examine these dynamics of change at the Apostle Islands by describing major changes in the personal characteristics of visitors, stability across time in their psychological evaluations of the Apostle Islands experience, and the emergent quality of boater behavior over the 22 year period of this study.

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Major Changes

Age

For social psychologists, age is seldom a very interesting variable. It is more often used as a control variable to deal with generational differences in perception and behavior. Dramatic changes in the age structure of users across the years, however, may be a critical factor driving the character of the Apostle Island boating experience. Our 1975 data (Figure 1a) show that most boaters were under the age of 40 (62%). Conversely, only 20% were in their 40s and 18% were over 50 years old. In 1975, boating at the Apostle Islands National Lakeshore was a relatively youthful type of experience. In 1985, the concentration of boaters under 40 had increased to just under 70%. Boaters in their 30s, however, made up an increasing majority of the boating population with 40% in their 30s, 17% in their 40s and 14% over 50. In 1997 the age distribution changed dramatically (figure 1c). The proportion of boaters in their 20s dropped from 30 to 13 percent, the percent in their 30's from 40 to 22 percent. The 40's became the modal class with 31 percent of the boaters in this age group. The percent over 50 went up to 35 percent. In 1975 63 percent of the boaters were under 40, and 70 percent of the boaters were under 40 in 1985. Twelve years later, 64 percent were over 40. The average age increased 8 years from 36 in 1985 to 44 in 1997.

Crowding

Within a cross sectional design, we usually look at the relationship between use level and perceived crowding by day during a single season or compare week ends or week days. Occasionally one can randomly assign to high and low density treatments (Heberlein and Kuentzel, in press). And as expected, when there are more people using the facility, people feel more crowded (Shelby and Heberlein 1986, etc.).

In 1976 there were 7,117 boater nights at the Apostle Islands. This increased to 15,828 in 1985. Between 1985 and 1997 use level only slightly increased to 16,540. So one might expect that the 1985 visitors would feel less crowded than the 1975 visitors. But this was not the case. Using a 4 item crowding scale (see McKinnell also Kuentzel and Heberlein, 1992) the average crowding level was significantly lower in 1985more visitors but less crowding. The average score in 1975 was 11.06 and the score in 1985 9.64 (p<.05). Why? Mckinnels analysis showed that most of this change could be explained by the changing visitor composition and by different preferences for contacts. The 1985 visitors were more likely to have no preferences for contacts and no expectations for how many boats that they might see while moored. In 1997 with only a small increase in use levels the 1997 visitors felt more crowded than the 1985 visitors using the 4 item scale 10.53 vs. 9.64 (p<.05). Using a 9 point scale (Shelby et. al. 1979) that was first used in the 1985 cross-section we also find that the 1997 visitors were significantly more crowded than the1985 visitors (3.10 to 2.38, p.<.05) Our preliminary analysis,

Page -5- Final June 28, 1999 following McKinnell, suggests that this is because the visitor population changed again, becoming older and more experienced with the islands. This was associated with clearer expectations and preferences for visitor contacts.

But there remain changes in the society which cant be explained by changing visitor characteristics. In the early days of the environmental movement, outdoor recreation management and research for that matter was occupied with solitude, crowding and the wilderness experience. Of the three groups we have studied, the 1975 visitors felt significantly more crowded than even the 1997 visitors even though use level in 1975 was less than half of the 1997 level.

These data show that crowding in actual recreation settings is more complex than a single cross section shows. As visitor mixes change, and as times change the carrying capacity threshold can also change.

Chartering

The Apostle Islands, a park service employee once noted, are logistically challenged. We certainly discovered that in our efforts to sample these visitors. To get to the islands overnight one needs a fairly large boat. Indeed being on a boat is the major part of the experience for thousands of visitors. The Apostle Islands are simply places to visit and stay overnight. But boats are expensive to purchase and dock space must be rented and in some cases is scarce. Boats spend most of their time at the dock as owners live and work elsewhere. One way of reducing costs is to put ones boat into the charter fleet. Here they can be rented to others for a two day minimum trip. Thus access to the islands is mediated by both owning and chartering boats. There were three major sources of charter boats at each time period.

In our surveys we asked respondents if they were on a chartered boat or a privately owned boat. In 1975 31% of the visitors were on charter boats, and in 1985 this more than doubled to 72% and in 1997 the percent chartering had dropped to 56 percent. The number of boats in the fleet had increased from 1975 to 1985. In 1997 the number of boats and charter days in three charter fleets had decreased substantially from the 1985 levels. The number of boats in the fleet is affected by tax law changes (reduced depreciation rates after 1986) and declining sales of one brand of yacht that provided the exclusive base of one of the rental companies.

One might expect that charterers are different than owners. Looking at the age of the charterers helps inform the age analysis. The 1975 data in figure 2a shows hat the charterers are much more likely to be in their 30's. In 1985 this was even more accentuated with 44 percent of those on chartered boats in their 30's.

In 1997 something very dramatic occurred besides decrease in chartering. The age distribution of those on private boats increase with the modal class now being those in the 40's.

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The age distribution of the charterers also increased. In 1985 13 percent of the charterers were 50 or over and in 1998 there were 29 percent over 50. The age and access processes (chartering) complimented each other.

Stability

Not everything changes over time. Here are two variable that remained constant even though the visitor population aged and access patterns (chartering vs owning) changed.

Income

It takes quite a lot of money to own a yacht. And the income distribution in America has become increasingly skewed between 1975 and 1997. One might expect that people charter because they dont have enough money to buy a boat. The number of older people is increasing and certainly older people have higher incomes or at least greater accumulations of wealth. Even so what might have been expected to change remained very stable. The average income standardized to 1992 dollars was $71,000 and there was no significant difference across the sample.

Simple ideas that charterers are poorer than people on private boats does not really hold. The distribution is bimodal. Charterers are likely to have both higher and lower incomes (figure 3). Yes, there are some people who charter who cant afford a boat. There are others who make plenty of money and dont want the hassle of owning a boat, or they may own a boat elsewhere.

Perception of Wilderness

In 1975 we asked people if they considered the Apostle Islands to be a wilderness. Sixty- two percent agreed with this assessment. Ten years later with a very different boater population, and at a very different time in our environmental history 64 percent said they thought it was a wilderness. In 1997 63 percent of the aging boaters said they thought it was a wilderness. In spite of twenty two years of change, and a changing population the general belief about this resource was that 6 out of 10 labeled it as a wilderness. (figure 4)

Processes

Things take time, it is often said. Or Time is what keeps everything from happening all at once. Time is simply necessary for processes to occur and continual monitoring is necessary to keep in touch with change in a dynamic system. Three processes at the Apostle Islands serve as examples of this.

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Invading Species

After 1985 our occasional visits to the Apostle Islands gave some new opportunities. In 1987 the senior author and his wife rented kayaks and took a guided trip from a new outfitter to go out and view the sea caves on the mainland shore. These had not been easily accessible by sail boat, and they were too far for the tour boat to reach. An outfitter began to market trips and train kayakers. By 1997, from a biological perspective, it looked like we had an invading species on the islands. A new group was getting to the islands in something other than sail boats, power boats or a tour boat. We designed a survey of those kayakers who we found on the islands in 1997. As graph shows when compared with boaters their first kayaking trip was in the 1980's or 1990's (figure 5 ). The kayakers had been visiting the area for some time, (figure 6) and began to adopt the new technology for visiting the islands. The kayakers are similar to the boaters in age, except the absence of over 60 kayakers. Their incomes are equally high. They are much more likely to be childless. The kayakers represent a new group, who can land at many places on islands. They tend to prefer the islands closer to the mainland and they do not require docks or harbors the way the sail and motor boaters do. Only by following an area over time can such changes be documented.

Displacement

A major motivation for this study was to determine what happened to users of a wild park as visitor numbers increased. Park visitation increased between 1975 and 1985 as expected and we looked to see if some users had been crowded out by this more than two-fold increase in overnight visitation to the Park. We found that even those most sensitive to crowding in 1975 had not been pushed out of the park by 1985 (Kuentzel and Heberlein, 1992). This was largely because the absolute user numbers were low and the level of psychological crowding compared to other areas was low. Those who were most sensitive to crowding in 1975, however, had subsequently been displaced to less frequented places in the Apostle Islands. Even with further increases in user numbers, solitude was still to be found on the islands. Among 1975 boaters, there were no substitutes for the Apostle Islands, and those people committed to the area and disturbed by growing crowds simply visited alternate, less-known sites around the Islands.

Between 1985 and 1997, use levels did not increase, fluctuating between 15,000 and 18,000 boater overnights a year. Without increasing crowds of boaters, we would expect there to be plenty of opportunity for someone who feels crowded to find a more isolated, less used anchorage. 1985 boaters, however, who felt more crowded were no more likely than anyone else to seek the isolated spots around the Islands in subsequent years. Moreover, those who felt crowded in 1985 were more likely to stop visiting the Apostle Islands in subsequent years. The 1985 boaters were less bothered by crowding (vague encounter expectations and preferences) and less experienced as boaters. Consequently, their commitment to Apostle Islands boating was less pronounced, and the easiest response to perceived crowding may have been to not return.

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Life Course Changes

What effect does marriage, divorce, changing jobs, moving, or illness have on outdoor recreation participation? In order to answer this we need to follow people over time as these events occur. The 1975-97 panel has had 22 years to experience these changes. Thirty six percent experienced a marital change becoming married divorced or widowed. Figure 7 presents the self reported effect on boating participation. All of these changes tend to reduce rather than increase participation. Divorce and being widowed reduced participation for 30 percent of those who had this life event. On the other hand nearly 70 percent of these marital changes had no reported effect on participation. Job and residence changes had a bigger effect than marital change on participation These changes decreased participation more than they increased it. (Figure 8) . The greatest effect was personal illness or the illness of a spouse about 20 percent of the 1975 boaters reported either personal or spousal illness. This reduced participation for 70 percent of those who had an illness and 60 percent of those whose spouse had an illness.

Conclusions

Comparison and change are the hallmark of science. By collecting data over time, with the multiple time series, and the repeated panels we have begun to more completely assess the visitation dynamics at one small US National Park. These comparisons have led to some clear conclusions -- conclusions that would not have been reached with out data over time.

1) National Park visitors can show dramatic changes in age distributions, which affects both what they do and how they perceive the resource.

2) More people can mean less crowding as both the visitor characteristics and society changes over time.

3) The institutional factors mediating access can change due to outside forces. This effects who gets to this particular park.

4) Not everything changes over time. In spite of major shifts in the visitor population adjusted income remained stable, so did perception of the resource as wilderness.

5) New technologies and new institutions can introduce new sets of visitors into parks.

6) Displacement over time depended on the characteristics of the base group. The committed 1975 boaters tended to stay at the islands even as use levels increased, and were internally displaced. The less committed 1985 boaters were less likely to return to the Apostle Islands and those who felt most crowded were less likely to return in 1997. Even intra site or

Page -9- Final June 28, 1999 inter site displacement is conditioned by the social and psychological characteristics of the base visitor group.

7) Life course changes generally reduce participation over time, but marital changes have the least effect, job changes a greater effect, and personal health problems have the largest effect.

Bibliography

Heberlein, T. A. & Kuentzel, W. F. (Forthcoming). Crowding, success, and satisfaction for doe and trophy buck hunting: The Sand Hill Experiments. Human Dimensions of Wildlife.

Heberlein, T. A. & Vaske, J. J. (1979). The Apostle Islands Visitor in 1975. Working Paper #11. School of Natural Resources, College of Agricultural and Life Science, University of Wisconsin - Madison.

Hellerstein, D. & Mendelsohn, R. (1990). Analyzing outdoor recreation over time. In: J. T. OLeary (Ed.) Proceedings of Outdoor Recreation Trends Symposium III.

Kuentzel, W. F. & Heberlein, T. A. (1992) Cognitive and Behavioral Adaptations to Perceived Crowding: A Panel Study of Coping and Displacement. Journal of Leisure Research, 24, 377-393.

Louviere, J. & Timmermans, H. (1990). Preferences analysis, choice modeling and demand forecasting. In: J. T. OLeary (Ed.) Proceedings of Outdoor Recreation Trends Symposium III.

McKinnell, T. A. (1986). Increasing use levels and perceived crowding at the Apostle Islands National Lakeshore: An analysis of change over ten years. Unpublished MS Thesis. Department of Rural Sociology, University of Wisconsin-Madison.

Peterson, G. L. & Stynes, D. (1985). The stability of a recreation demand model over time. Journal of Leisure Research, 23, 209-224.

Shelby, B. B. & Heberlein, T. A. (1986). Carrying Capacity in Recreation Settings. Corvallis, OR: Oregon State University Press.

Shelby, B. B., Vaske, J. J., & Heberlein, T. A. (1989). Comparative analysis of crowding in multiple locations: Results from fifteen years of research. Leisure Sciences, 11,269-291.

Stynes, D. J. & Driver, B. L. (1990). Trends in measurement of beneficial consequences of leisure. In: J. T. OLeary (Ed.) Proceedings of Outdoor Recreation Trends Symposium III.

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Methodological Appendix 1997 Methodology

Field Sampling Strategy

The Apostle Islands National Lakeshore presents a substantial logistical challenge for a researcher gathering a representative sample of overnight visitors to the area. The Apostle Islands National Lakeshore includes 21 islands on the Northern tip of Wisconsin within roughly a 600 square mile area of Lake Superior. Boaters, who travel primarily in sailboats, power boats, and sea kayaks, move at various paces between the islands. They stop frequently to sunbathe or beach comb on a deserted sandy beach, visit the many historic sites (light houses, fish camps, logging camps, quarries), participate in Park Service interpretive programs, hike the many trails on the islands, or picnic on the islands. At night, they may choose to anchor in a protected bay, tie to a Park Service dock, or camp at a designated campsite on one of the islands. The boater population therefore is a moving target and the distance over water that is necessary to contact them, coupled with Lake Superior weather make sampling a challenge.

From previous sampling experience (1975 and 1985 studies), the most comprehensive sampling plan calls for onsite contacts. Exit surveys are less reliable because of a growing number of marinas in the area. More importantly, many boaters either trailer their boats to the area or travel across water to the Islands from other Lake Superior ports. Therefore, we had to position census workers at those locations where boaters typically spent the night. To sample overnight visitors, we transported individuals to various locations around the Islands, set them up in campsites, provided them with a personal water craft (sea kayak, dinghy, or canoe) to row out to moored boats, and asked them to gather the names and addresses of all boaters docked, anchored, or camped overnight on that island.

Fortunately, there are a limited number of bays that are consistently protected well enough from rough weather or changing winds. Many other anchoring bays exist, but either provide poor anchorage or face open water. So the majority of the overnight sail boat and power boat use is limited to 7 sites: Presque Isle Bay and Quarry Bay on Stockton Islands, , South Twin Island, , Raspberry Island, and . Nevertheless, these sites are scattered throughout the archipelago, and the challenges of increasing distance and weather interact as one leaves the mainland.

To transport census workers to the islands, we employed three boat options. First, we used a local water taxi service to drop off and pick up people at each of the sampling sites. This method, however, was cost prohibitive ($69 per hour), especially with the stratified random sampling procedure used, which required 48 drop offs and pick ups during the summer. Second, we used Park Service transport when our sampling schedule fit their pre-existing boat schedules. Park Service boats however would not transport sea kayaks or canoes, but would only take deflated and folded dinghys. Finally, we used a research boat owned by Sea Grant, our funding organization. This required that we maintain and operate a boat suitable for Lake Superior conditions. Lake Superior weather requires that one pay close attention to marine forecasts that report wind conditions, wave condition, fog conditions, and warn of impending squalls and storms moving through the area. Lake Superior boating therefore requires extra attention to boat safety, GPS navigational techniques, wind directions, and boat maintenance.

Overall, visitor contact in our sampling strategy is not a straight forward process. It requires that one become immersed in the Great Lakes "boat culture," and it requires a degree of logistical mobilization and coordination unique to the requirements of safe boating in Lake Superior.

Sample Design

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The 1997 sample employed a stratified random sample that was proportionate to overall overnight boater use of the Apostle Islands. The design used 1996 Park Service visitor counts to devise a sample selection procedure. We stratified the sample on three dimensions. First the sample was stratified based on the low use or shoulder boating season (June and September) and high use season (July and August). Table 1 shows that one fourth (24.8%) of the 1996 overnight visitors came in the shoulder months of either June or September, while three fourths of the sample (75.2%) visited during the high use months of July and August. Only 5% of the 1996 overnight boaters made visits during months outside of this 4-month boating season.

Table 1. Proportion of overnight visits in the high use season and low use season - From 1996 Apostle Island National Lakeshore visitor counts. # of Overnight Visitors Proportion of Total Use Low Use (June, September) 3869 24.8% High Use (July, August) 11,739 75.2%

The sampling design also stratified by overnight use at each of the islands. Table 2 shows that use is concentrated at only a few of the islands. Because of boaters desire to find well protected anchorages, 92.78% of the overnight boater visits were recorded at only 6 islands: Stockton, Rocky, South Twin, Raspberry, Sand and Oak. contains two protected bays where overnight boaters frequently anchor: Presque Isle bay, which had 44.8% of the total 1996 overnights, and Quarry Bay, which had 10.34% of the 1996 overnight visits. The sample selection process was therefore built around these 7 sites. The few people who anchored at places like or York Island (just over 7%) did so because weather conditions were just right on that particular night. We then assumed that because most trips in previous studies were multi-night trips, these people were just as likely to be selected at one of the 7 sites on a subsequent night of their trip. We therefore placed as many as 5 people in the field on any given sampling day: 1 person at Sand, 1 person at Raspberry, 1 person at Oak, 1 person at Stockton who covered both Presque Isle and Quarry Bays, and 1 person at Rocky and South Twin, which are approximately a mile apart.

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Table 2. Proportion of overnight visits by Island - From 1996 Apostle Island National Lakeshore visitor counts. Island # of Overnight Visitors Proportion of Total Use Basswood 76 0.49% Bear 136 0.87% Cat 64 0.41% Devils 131 0.81% Hermit 20 0.13% Ironwood 36 0.23% Long 0 0.00% Manitou 153 0.98% Michigan 42 0.27% Oak 631 4.04% Otter 248 1.59% Outer 49 0.31% Raspberry 1148 7.36% Rocky 2157 13.82% Sand 1056 6.76% South Twin 884 5.66% Stockton 8607 55.14% York 170 1.09% Note. The Park Service prohibits camping or mooring near Eagle, Gull, or North Twin Islands.

Next, the sample was stratified by weekday use (Sunday through Thursday nights) and weekend use (Friday and Saturday nights and holidays - July 4th and Labor Day). Table 3 shows Park Service daily counts for the total number of boats that visited the islands on weekdays and weekends during both the low use months (June and September) and the high use months (July and August). The proportions shown in this Table are percent of total use of the islands. As expected, weekend days (Fridays and Saturdays) received slightly more of the total 1996 overnight visits than weekdays (Sunday through Thursday nights), with a ratio of 1 weekday for every 1.45 weekend days in the low-use season, and 1 weekday for every 1.08 weekend days in the high-use season.

Table 3. Total number of boats by low-use/high-use seasons and by weekends/weekdays in 1996. Low Use Season High Use Season

Weekdays Weekends Weekdays Weekends

Boats % Boats % Boats % Boats % Presque Isle 177 4.50% 228 7.40% 614 15.80% 729 18.70% Quarry Bay 90 2.30% 70 1.80% 126 3.20% 117 3.00% Rocky/South Twin 65 1.70% 133 3.40% 242 6.20% 301 7.70% Raspberry 13 0.30% 29 0.70% 123 3.10% 122 3.10% Oak 10 0.20% 11 0.30% 53 1.30% 84 2.10% Sand 31 0.80% 35 0.90% 117 3.00% 81 2.00% Other 35 0.90% 40 1.00% 123 3.10% 84 2.10% Total 421 10.70% 546 15.50% 1398 35.70% 1518 38.70% Note. These proportions contain some rounding error.

In summary, the sampling procedure was based on 1996 visitor use statistics provided by the Apostle Islands National Lakeshore. Our goal was to stratify the sample proportional to use based on three criteria: 1) low- use/high-use seasons, 2) proportion of overnight use by islands, and 3) weekdays/weekend days. These criteria

Page -13- Final June 28, 1999 dictated that we randomly allocate one-fourth of our 1997 sampling days to June and September (low-use season), and three-fourths of our sampling days to July and August (high-use season). The stratification criteria also called for allocating approximately 41% of the sampling days to weekdays (Sunday through Thursday nights) and 59% of the sampling days to weekend days (Friday and Saturday nights and holidays) in the low-use season. In the high-use season, we established a nearly equal number of sampling days on weekdays (48%) and weekend days (52%). Finally, we sampled on an equal number of days at each of the established sampling sites to reflect the differential proportions of people who stayed overnight at these 5 Islands.

Sample Schedule

The next step of sampling was to create a sampling schedule that reflected these stratification criteria. The goal of the sampling procedure was to over-sample based on 1996 use statistics, so that when we drew a final sample based on 1997 use statistics, we would have enough people in each of the stratification cells, given all the contingencies of the census process. The 1985 Apostle Island study sampled each Island 4 days in the low-use season, and 10 days in the high use season. With this schedule, they were able to census a total of just under 1200 boaters, and therefore come up short on a few of the stratification cells when they drew the final sample that was sent questionnaires. Therefore, our target was to census at least 1500 sail boaters and power boaters, and as many sea kayakers as we encountered during the 1997 season. We therefore decided to increase the 1997 sampling days to 18 days at each island - 5 days during the low-use season and 13 days during the high-use season. This meant sampling 3 weekend days and 2 weekdays at each Island during the low-use season, which meant approximately 1 trip to each Island in June and 1 trip to each in September. We also scheduled 7 weekend days and 6 weekdays of sampling at each Island during the high-use season, which meant approximately 2 trips to each Island in July and 2 trips to each Island in August.

Because of the many contingencies of sampling at the Apostle Islands such as high seas, fog, sick workers, unreliable workers, or boat maintenance problems, we did not always reach these targets for each of the Islands. Table 4 shows the actual number of days sampled at each of the sites. This Table shows that the number of days sampled during the high-use season was reasonably close to the original schedule. The only Island undersampled during July and August was Oak. The sampling went a little less smoothly during the low-use season. Sand was not sampled at all, Rocky was undersampled, and Raspberry was oversampled on weekend days during the low use season. During this low-use season, June suffered because of boat problems and the learning curve of coordinating the sampling process. The September sampling season suffered because of some severe weather. When there is bad weather, there are no boaters to census. Otherwise, our actual days of sampling during the 1997 season came close to the target number of days of sampling.

Table 4. Actual number of sampling days at each of the 5 sampling sites during the 1997 season. Low Use Season High Use Season

Weekdays Weekends Weekdays Weekends Stockton 2 3 7 6 Raspberry1475 Oak 2 2 5 1 Rocky 1 2 6 7 Sand0066

Census Counts

The sampling procedures employed in this study yielded a census of 1802 boaters during the 1997 season. This total included 809 passengers on sail boats (62%), 198 passengers on power boats (15%), 228 people with sea

Page -14- Final June 28, 1999 kayaks (18%), and 64 people in Voyageur Canoes (5%). There were another 503 people in unspecified crafts. These were names gathered before we instructed the census workers to specify whether respondents were in sail boats or power boats. We also gathered 840 names from Stockton Island (46.6%), 355 names from Rocky/South Twin (19.7%), 242 names from Raspberry (13.4%), 198 names from Oak Island (11.0%), and 167 names from Sand (9.3%). Table 5 also shows the number and percent of boaters gathered by island, season, and weekday/weekend.

Table 5. Total number of people in the 1997 census by island, low-use/high-use seasons, and weekends/weekdays. Low Use Season High Use Season

Weekdays Weekends Weekdays Weekends

People % People % People % People % Stockton 12 0.006% 122 6.7% 218 12% 488 27.0% Rocky/South Twin 23 1.3% 11 0.006% 57 3.1% 275 15.2% Raspberry 1 0.001% 44 2.0% 83 4.6% 114 6.3% Oak 8 0.4% 16 0.008% 115 6.3% 59 3.3% Sand 0 0% 0 0% 87 4.8% 80 4.4% Total 44 2.0% 182 10% 560 31% 1016 56%

With all the contingencies of sampling at the Apostle Islands, our census during 1997 did not fit the stratification categories very well. When comparing Table 5 with Table 3, one can see that our 1997 census oversampled high-use season visitors and undersampled low-use season visitors. Overall, the full 1997 census oversampled boaters at Raspberry, Oak, and Sand Islands, and undersampled boaters at Stockton Island. Finally, the census oversampled boaters on weekend days and undersampled boaters on weekdays. It was these contingencies of sampling that motivated us to census 3 times the number of people that would receive a mailed questionnaire. With the number of boaters oversampled in each stratification category, we could the send a follow-up questionnaire to a sub-sample of boaters who matched the proper proportions generated from 1997 Park Service boater counts.

Selecting From The Census

In selecting a final sample of people to receive mailed questionnaires, we obtained the 1997 boater counts from the Park Service in October of that year. In the final selection, we stratified on only 2 dimensions: low- use/high-use seasons and by island. We chose not to stratify on weekdays and weekend days because in 1985, the average trip length was 4 days, so most people made trips across both weekdays and weekend days. Further, only 60 people out of 377 in that sample (16%) made weekend-only trips during the 1985 season. Even fewer - 55 people or 14.5% - made weekday- only trips during the 1985 season. Therefore the census strategy used in the 1997 study should have been able to account for those who take weekend only or weekday only trips, in spite of the fact that only 34% of our census were contacted on weekdays during the 1997 season.

We next established our sample size base on Park Service boater counts for 1997. Table 6 shows the ratio of use in 1997 by Island and by season. Our stratified sample attempted to replicate the ratios as closely as possible. The selection of a sample size was constrained by the cell with the lowest number of names. Table 6 shows that our census during the low-use season was the biggest constraint. In our sample selection, we slightly undersampled Rocky and Sand, and slightly oversampled Raspberry and Oak during the low use season. The remaining cells followed the Park Service ratios fairly closely. With this established sample size, we then randomly drew names from each of the cells of the sampling framework. Duplicate names and duplicate households were replaced in the selection process.

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Table 6. Sample size selection based on 1997 Park Service boater counts. National Park Service 1997 Sample

Low-Use High-Use Low-Use High-Use

# Boats % # Boats % People % People % Stockton 516 14.19% 1701 46.79% 81 14.34% 263 46.55% Rocky/South Twin 157 4.32% 474 13.04% 8 1.42% 78 13.81% Raspberry 39 1.07% 247 6.79% 18 3.19% 40 7.08% Oak 63 1.73% 174 4.79% 14 2.48% 32 5.66% Sand 40 1.10% 225 6.19% 0 0.0% 31 5.49% Total 44 2.0% 182 10% 560 31% 1016 56%

     

A stratified random sample of 565 sailors and power-boaters was drawn from the 1802 boaters contacted in the summer of 1997. On December 22nd of that year, a 32-page questionnaire was sent to these 565 people. On January 7th, 1998, a postcard reminder was sent to all respondents, and on February 16th a second survey and cover letter were sent to the 282 respondents not yet heard from. This second wave yielded 57 more responses. In May and June, non-respondents were contacted by phone and asked if they would be willing to fill out the questionnaire if sent a new copy; those who repsonded negatively were asked their reason. Those who responded positively were sent another questionnaire, and this was considered the third wave. Nineteen additional surveys were returned. Finally, the questionnaire was shortened to 20 pages and sent out with a new cover letter to the remaining on  After the last surveys were returned on October 12th and January 15th(!), the final return stood at 389 out of 562 (3 were removed from the original sample as they turned out to be kayakers) or 69.2%. When the original n is adjusted by removing the undeliverable surveys and deceased respondents, the adjusted percent return becomes 389 out of 557, or 69.8%.

1997 Cross-Section of Kayakers

On March 16, 1998, 28-page questionnaires were sent to all 195 sea-kayakers contacted in the islands during the summer. This mailing yielded 69 returned surveys, only 36% compared to the 50% received by boaters in the first wave. The reminder postcard was sent on April 15th, and the second wave mailing on May 11th. Fourteen additional responses were received. Just as for the boater group, a shortened questionnaire (20 pages) was sent as the third wave on Y, and 20 more surveys were returned. The final count was 103 out of 191 (4 were removed because they turned out to be sailors or power-boaters rather than kayakers) or 53.9%. When the deceased and undeliverables are removed, the adjusted response rate is 103 out of 184, or 56.0%.

Tracking Procedures for 1975 and 1985 Panel Respondents

The process of relocating 1975 and 1985 respondents began in August 1997 and continued until April 1998. A database was created to keep track of the status of each person. The first stage was to look up each respondent at their former addresses. This was done using CD rom APhone Discs@(?) and internet search engines AFour One One,@ AWhoWhere@ and AInfoseek.@(?) If a respondent was still at the same address, or had moved but was easily identifiable (i.e. an unusual last name in a small town), then they were marked as Afound@ in the database. If the search engine revealed more than one listing that could conceivably be the respondent in question, then they were marked Ato be called.@ In the 1975 and 1985 surveys, respondents were asked to give the name of a relative and a friend who would know their location in the future. If the search for the respondent=s own name yielded nothing,

Page -16- Final June 28, 1999 then these friends and relatives were looked up using the same method. If a phone number was found, then the friend or relative was marked Ato be called.@ If nothing was found at all, the respondent was marked Asearch@ and left with little hope of being located.

Phone calls were made in a systematic fashion. As each number was tried, wrong numbers and wrong people were eliminated from the list, so that at the next attempt the caller would have fewer options. If the respondent was reached, or a relation who was willing to provide the former=s address, then (s)he was changed to Afound@ in the database. If a relation informed us that (s)he had passed away, his/her status was marked Adeceased.@ If none of the calls were fruitfull, then the respondent was marked Asearch.@

646 boaters were surveyed in 1975, of which 472 had been successfully relocated in 1985. In April 1998, at the end of the above-described tracking process, 411 of the total 646 respondents were found. An additional 33 were located with some degree of uncertainty: either confirming phone calls did not go through, or the best bet appeared to be to send the survey to a friend or relative of the respondent. In any case, these additional 33 respondents were included in the mailing, bringing the total number of located respondents to 444. Divided by the original 1975 n of 646, this is 68.7%. Thirty were found to be deceased, however, which brings the percentage up to 72.1%. Moreover, when one considers only those respondents who had been tracked down in 1985, the 1997 search located 369 out of 472, or 78.2%. Of those who had not been found in 1985, our search located 75 out of 174, or 43.1%.

The same process was used to locate the current addresses of the 1985 respondents. However, this group proved simpler since they had only been surveyed once before. When all of the computer searches had been done and all the phone calls made, 326 respondents out of the original 490 were located. An additional 38 were found with some degree of uncertainty. Four more were reached by phone yet declined to participate, and so were excluded fom the mailing. The 364 boaters included in the 1985-1997 panel made up 74.3% of the original group of 490. When the two deceased respondents are removed from the total, this percentage increases slightly to 74.6%.

1975 Panel Surveys

On April 17, 1998, questionnaires were sent to the 444 1975 respondents who were located. As described above, 33 of these were located with some degree of uncertainty. In those with uncertain addresses, a postcard was enclosed to be returned in case it was the wrong person. Those that were sent care of a relation included a stamped envelope for them to forward the questionnaire on to the respondent. After the first mailing, 181, or 40.8%, were returned. A postcard was sent on May 13th, and the second survey mailing went out on June 1st. Fifty more were returned. A shortened questionairre (from 27 to 22 pages) was sent on Y and 21 more were received, adding up to a final 252 out of 444, or 56.8%. When adjusted to include only those respondents who received the survey, the response rate is 252 out of 409, or 61.6%.

1985 Panel Surveys

The 1985 panel follow-up survey was sent on April 23rd to 364 respondents. Of these, 38 were sent either to an uncertain address or to the care of a relative or friend. This initial mailing yielded 92, or 25.3% resopnse. A reminder postcard was sent on May 13th, and the second wave of surveys went out on June 1st. 48 more were returned. The final wave was a shortened 22-page version of the questionnaire, which was sent on june first and yielded an additional 20 returns. The final percentage, then, was 160 out of 364, or 44.0%. The adjusted response rate was 160 out of 327, or 48.9%.

Weighting Procedures

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As previously described (see field method section), the 1997 sampling design employed a stratified random sample that was proportionate to overall boater use of the Apostle Islands during that summer. The sample was drawn in proportion to the distribution of boat-days at each island and within each of the four time strata. Boat-days, however, are not the same thing as boaters, and the study required a random sample of boaters. Boats (boaters) spending more days in the Islands had a higher probability of being in the sample than those spending fewer days. Therefore, it was necessary to compensate by weighting each boater in inverse proportion to the number of days (s)he spent in the Islands. For example, a boater spending ten days in the Apostles should get a relative weight one fifth as large as a boater spending only two days. Such a weight was created using the following formula:

Weight = (WD*N)/W Where WD = 1 / # of days in the islands, W= sum (WD), and N = the sample size.

For cases with missing data for number of days, median substitution was employed. This weighting procedure was applied for both the 1997 and 1985 cross-sections of boaters, as they had the same sampling design. The 1975 sample, however, was achieved by obtaining lists of boaters and survey boat owners for a list of everyone who was on the boat over the summer season. Thus length of trip would not be likely to effect the probability of being in the sample as it does for on the water sampling methods. Consequently each 1975 respondent was simply given a weight of A1@.

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