Estimating Public Use of the National Park System to the Year 2000
It is often estimated that the 1960 population of the United States will almost double by the year 2000. Outdoor recreation activities generally are increasing at twice the rate of population growth. According to the Bureau of Outdoor Recreation's most recent survey, outdoor recreation activities will double their 1960 figure by 1980 and quadruple it by 2000. This is because leisure time, income and mobility are all increasing much more rapidly than population. But travel to the National Park System is one of the fastest growing segments of outdoor recreation. The 1960 National Park System travel total will have doubled by 1967 instead of 1980 and will have more than quadrupled by 1976 instead of 2000. The growth rate for National Park System travel is such that a travel year of one billion by 2000 no longer appears fantastic.
a. Population Growth. In 1960 the population of the United States was 179,000,000. A widely accepted estimate for our population in the year 2000 is 350,000,000. This means the 1960 population will have approximately doubled by the end of the century unless widely discussed possibilities of population control materially alter current trends. It is always possible that the gravity of unrestrained population growth will eventually bring control that will ease the problem of growing public use of the National Park System. So much of growth in park use comes from other factors than population that we believe the basic analysis in this study will probably remain generally sound under foreseeable conditions. If National Park System travel increases in direct proportion to population, it will rise from 72,000,000 in 1960 to 144,000,000 in 2000. That figure was exceeded even in 1967. We must, therefore, look further.
b. Increases in Outdoor Recreation. ORRRC's National Recreation Survey made projections for all outdoor recreation activities in the United States to the year 2000. Those projections have now (1967) been up-dated by the Bureau of Outdoor Recreation to reflect the results of a comprehensive follow-up survey of summertime outdoor recreation activities for 1965.  These projections show that outdoor recreation activities in the United States will increase far more rapidly than population during the rest of the century. While population will almost double by 2000, outdoor recreation will double by 1980 and quadruple by 2000. In other words, outdoor recreation activity is increasing at least twice as rapidly as population. This is because leisure, mobility, and income are increasing much more rapidly than population.
Passive outdoor pursuits will more than double their 1960 figure by 1980 and triple by 2000, which is somewhat slower growth rate than outdoor recreation as a whole. However, sightseeing, one of the principal activities in the National Park System, will more than double by 1980 and quadruple by 2000. Walking for pleasure, another important activity in the System, will grow even more rapidly, almost tripling by 1980 and increasing four and one-half times by 2000.
Backwoods recreation will also increase rapidly. Camping will almost triple by 1980 and quintuple by 2000. Hiking will more than double by 1980 and almost quintuple by the end of the century.
Water sports show some variations. Fishing will increase one and a half times by 1980 and only about double by the year 2000. Boating, however, will more than double by 1980 and quadruple by the year 2000. Swimming will multiply almost two and one-half times by 1980 and more than quadruple by the year 2000.
Physically active recreation of youth will grow rapidly, tripling by 1980 and quintupling by 2000. Bicycling will almost triple by 1980 and quadruple by 2000. Horseback riding will grow rapidly but not as fast as outdoor games and sports, which will multiply almost six times by 2000.
Considering these various special growth rates collectively, if public use of the National Park System increases in direct proportion to outdoor recreation in general, it will double from 72,000,000 in 1960 to 144,000,000 in 1980, and quadruple to 288,000,000 by 2000. This would represent something less than doubling 1967 travel by the end of the century. We know, however, that travel to the National Park System is already increasing much more rapidly than that. It is growing not only at a much faster rate than population, but also at a much faster rate than outdoor recreation generally.
c. Public Use of National Park System.
(1) Estimates by Marion Clawson in 1959. In an extremely perceptive paper called "The Crisis in Outdoor Recreation," published in 1959, Marion Clawson differentiated between user-oriented recreation areas located quite close to people who use them, such as city and county parks; intermediate recreation areas which are relatively accessible but contain more natural environment, such as state parks and reservoir areas; and resource-based recreation areas, including outstanding examples of natural beauty, whether of mountain, lake, forest or desert, and unique historic and scientific sites. The principal areas in this last category, he pointed out, are the National Park System and the national forests.
Marion Clawson then attempted to estimate the probable growth in demand for each of these three types of recreation areas by 2000. His results are very interesting. His starting point was an estimated ten-fold increase in the total demand for outdoor recreation between 1950 and 2000. He then estimated that public demand for user-oriented recreation areas would quadruple between 1950 and 2000; for intermediate areas it would increase sixteen times; but for resource-based areas, such as the National Park System, public demand might well multiply forty times between 1950 and 2000.
The reasons Mr. Clawson gave for believing the growth rates would vary are very interesting, although sketchy. He considered that two factors--large urban population and more leisure time--would increase the demand for user-oriented areas, but that two other factors--higher incomes and greater mobility--would have little importance for this type of area. In fact, he conjectured that these forces might tend to divert more prosperous and mobile seekers of outdoor recreation to places farther from home, He foresaw a much greater increase in demand for intermediate areas because of large rises in average income and annual travel But he concluded that "lack of time and money still keeps many families from trips to distant national parks and forests. With higher family incomes and longer vacations, the potential demand in the year 2000 may well be forty times what it has been in the recent past." 
(2) Estimates by the National Park Service, How does the actual experience of the National Park Service compare with these estimates? What public use of the System does the Service now project for the future?
For eight years since Marion Clawson's 1959 predictions, visitors have been pouring into the National Park System, If one uses 1950 as a base, as he did, total travel to the National Park System was 33,000,000. By 1960, this number had increased to 72,000,000, and by 1966, to 133,000,000. In other words, travel has multiplied over four times in sixteen years.
In April 1967, the Service issued to its key officials, for in-Service use, projections of visits to the National Park System through 1976.  In this valuable document, it is estimated that travel to the System will total almost 347,000,000 by 1976, representing a ten-fold increase over 1950. The National Park Service has not carried its own projections for the System beyond 1976, but its statisticians are well aware of the serious nature and tremendous dimensions of the long-time travel trend as seen today.
Of course, one must remember that part of the increase in travel to the National Park System represents new areas. Nevertheless, the projections for increases in travel to some of the long-established areas are sufficient to reveal how general the increases are. The following table presents data for some well-known areas in each category of the System:
Any projected figures for the year 2000 would, of course, be highly conjectural. A mathematical projection of the 1950-1976 trend to the year 2000 is not presently available to this writer. It appears to be the case, however, that 1950 travel to the National Park System will have multiplied something like ten times by 1976, to a total of 347,000,000. If there were to be another ten-fold increase during the next 26 years, travel would rise by the year 2002 (only 34 years away), to the astronomical (and ridiculous) figure of 3,470,000,000, or 100 times 1950 travel. These fantastic figures suggest, however, that it would not be prudent to laugh Marion Clawson's rough conjecture of 40 times 1950 travel by the year 2000 entirely out of the ball park. A National Park System travel year of one billion visits, or three times 1976 travel by 2000, no longer seems fantastic.