Americans are giving their public libraries a workout. According to a new national survey, circulation at public libraries increased more than twice as much as the population during the last four decades.
The survey, based on a sample of 53 libraries serving at least 25,000 patrons each, was conducted by Herbert Goldhor, director of the Library Research Center at the University of Illinois. Dr. Goldhor notes that loans of library materials shot up 160 percent between 1941 and 1982, while population nationwide increased only 70 percent.
His survey offers no explanations. But in a phone interview, Goldhor says one logical reason is the fact that many public libraries have new and more attractive facilities, with ample space for reading and cultural programs.
Another reason, he says, is that they are offering a wider mix of materials, including video cassettes, records, films, and, in some cases, take-home microcomputers. Also, he notes, more Americans are generally better-educated now than 40 years ago.
Goldhor also says he believes a change of attitude on the part of many librarians has played an important role.
''I think librarians are more user-friendly, to use the computer term. They're setting more convenient hours and giving better service. And they're building more balanced collections, giving people less of what librarians think they ought to have and more of what people really want.''
For years, Goldhor says, many librarians tried to market books according to what they thought their patrons should read. They didn't want to invest in any ''ephemeral'' books that might not remain relevant over time. But by various means, including leasing best sellers from rental companies, librarians are making available more currently popular materials.
The ''classics'' and research materials, previously stocked in every branch, now often are largely confined to a city's central library. When someone in a branch wants to check out a copy of ''Ivanhoe,'' for instance, he or she might have to wait a bit longer to get it.
Library circulation of materials for children has risen during the last 10 years. But circulation of these materials, as a percentage of the general increase in loans during the period studied in the Illinois survey, is down. As a fraction of total circulation, juvenile materials hit a high of 51 percent in the late 1950s and now stand at only 31 percent. But Goldhor sees no cause for alarm. He points to better school libraries, more television-watching, and fewer children.
''You can't say anything is wrong - the thing that's remarkable is that the adult circulation has increased so much.''
Goldhor emphasizes that individual libraries vary - many are losing circulation and others have been forced to cut back on purchases. But libraries that can afford to keep buying new materials are ''having a field day.''
Many libraries do have severe budget problems and have been forced to cut back. A recent study by Ken Shearer, a professor of library science at North Carolina Central University, notes that the average US library spent 14 percent of its operating budget on materials in 1981, compared with 19 percent in 1970.
Another study, by the R. R. Bowker Company, shows the average price of a hard-cover library book has increased during the last five years from $19.22 to
Some libraries now have begun to charge user fees - particularly for reserve services and computer searches for subject matter - to help make ends meet. A heavier reliance by most on interlibrary loans is also helping.
Although some of the newer materials, such as video cassettes, are costly, Goldhor says the cost per unit of use may actually be lower than for books, which can wear out swiftly and may be used less often.
But for anyone who suspects that audiovisual materials may be slowly edging books off the shelves of the nation's libraries, Goldhor offers this assurance:
''They're not displacing books - I would estimate that 90 percent of the circulation now is in books. If anything, I think libraries have been sort of disappointed that audiovisual materials haven't become more popular. The idea originally was that young people would be more attracted, but they tend to be used by the same people who borrow books.''