Next month, Carol Vaughan will leave her large, prairie-style frame house in Fort Worth, Texas, for her annual trip to a reunion in St. Louis. She'll pay $ 138 for her round-trip flight.
Five years ago such a ticket cost her $230.
Why the decrease? Airline deregulation, phased in under a bill signed by President Carter in 1978, now allows air fares to be set not by federal regulators but by market rates - which, at least between major markets, has resulted in substantial drops in prices.
And why deregulation? Many observers point to research on regulatory reform done by economists and transportation specialists in the nation's public-policy research organizations.
These organizations - commonly known as ''think tanks'' - began seriously studying the economic impact of regulation in the mid-'60s. By the late '70s, the ideas generated at such venerable organizations as the Brookings Institution , the Hoover Institution on War, Revolution, and Peace, and the American Enterprise Institute for Public Policy Research (AEI) had gained sufficient weight to be translated into law.
For Miss Vaughan and millions like her, the results have been direct and tangible - demonstrating once again the power of ideas, and of the think tanks behind them, in American civic life.
To examine how such policy-shaping ideas are produced and disseminated in contemporary American society is to focus largely on the nation's think tanks - especially those that wrestle with the issues facing the nation's political leadership. Little understood by the public at large - and sometimes confused with consulting firms, contract research corporations, lobbying groups, political-action committees, and the multitude of other idea-processing organizations of the so-called ''information age'' - these public-policy think tanks exert considerable influence on American political life:
* Some 20 scholars and associates from AEI are now serving or have served in the Reagan administration. The Heritage Foundation has supplied 12 others. More than 40 current and past fellows of the Hoover Institution are serving on various governmental advisory panels.
* There is also a steady reverse flow of scores of former public officialsinto think tanks. Former President Gerald R. Ford is now with AEI; former Secretary of State Henry A. Kissinger is now with the Center for Strategic and International Studies at Georgetown University; and former Interior Secretary James G. Watt spent his first three months out of office with Heritage. Alice Rivlin, who left Brookings in 1975 to become the first director of the Congressional Budget Office, returned to Brookings last year.
* This January, Brookings and AEI will conduct a joint briefing in Williamsburg, Va., for newly inaugurated freshman congressmen, under the aegis of the Congressional Research Service. Before President Reagan's China trip last spring, Brookings staff members briefed the White House press corps to orient them on the major issues they should expect to encounter.
* Not surprisingly, the ideas generated in think tanks can directly influence the nation's course. A publication by Heritage (''Mandate for Leadership: Policy Management in a Conservative Administration'') was praised by presidential adviser Edwin Meese III at a Washington breakfast meeting shortly after the 1980 election as the blueprint for administrative action. President Reagan later observed that ''the Heritage Foundation's research continues to be useful to us and to our policymaking process.''
A kind of university without students, the typical think tank is a nonprofit organization of ''fellows,'' or scholars, from various disciplines. Many of the hundreds of think tanks in existence (reportedly more than 75 in Washington alone) focus on particular areas - health issues, defense, technological development, and so forth. Even within the sphere of public-policy think tanks, certain ones work within defined areas: The Urban Institute, for instance, works primarily on problems affecting cities, while the Joint Center for Policy Studies undertakes research on issues of specific interest to black Americans. But what might currently be called the ''big four'' of public-policy think tanks - Brookings, AEI, Heritage (all based in Washington), and Hoover (based at Stanford University in Palo Alto, Calif.) - cover a broad range of topics. Collectively, they address most of the major legislative issues facing the nation - issues that come into particular prominence during an election year.
Some think tanks, like Brookings and Hoover, are striving to move away from ideological labels and to escape the (respectively) liberal and conservative tags fastened on them over the years. Others, like Heritage and the Cato Institute on the right, or the Roosevelt Center and the Institute for Policy Studies on the left, are known for their more clearly ideological stances. Under federal law, however, a think tank risks losing its tax-exempt status if it becomes a lobbying group for a specific position. Its function, instead, is one of researching and publishing - of finding ways, as Brookings executive vice-president Roger D. Semerad says, to ''get ideas into the mainstream, so that when the time comes, you're ready.''
That emphasis on ideas that have an impact on public policy aligns these think tanks with their close cousins, the contract and advisory research organizations like SRI International in Menlo Park, Calif., and the Rand Corporation in Santa Monica, Calif. Unlike many public-policy think tanks, however, SRI does substantial amounts of private research paid for by their clients and not immediately made public. ''We cringe every time someone calls us a think tank,'' says Allan Lee, senior director of the SRI planning office. ''We're an applied research organization. We try to solve problems through encouraging the use of technology in society.'' Rand, which does 85 to 90 percent of its work for the federal government, essentially follows the government's agenda. ''Because we are contract based,'' says David Lyon, a Rand vice-president, ''we tend to be very much more closely linked into client contacts'' than Brookings, Hoover, or AEI.
Another distinction is size. Rand employs 500 researchers on a budget of over $48 million. SRI has some 2,000 professionals in laboratories and offices around the world doing some $200 million worth of business this year - a far cry from the neighboring Hoover Institution, whose staff of about 70 scholars operated on a 1983 budget of $10 million at its single California location.
A steady focus on what Mr. Semerad calls ''the mainstream'' is what most distinguishes public-policy think tanks from another set of close cousins, the universities. Like universities, think tanks frequently hire full-time professionals - although some lean heavily on associates who, though affiliated with the organization, also hold employment elsewhere. Like universities, too, the think tanks operate as nonprofit organizations, drawing funding from foundations and donations. But the goals tend to be different. ''The university professor is the theoretician,'' notes Herb B. Berkowitz, vice-president for public relations at Heritage, while ''we are the practitioners.'' Researchers in issue-oriented think tanks tend to look on university research as the appropriate tool for establishing basic economic or social models, or for engaging in purely historical studies. But a think tank, says Brookings president Bruce K. MacLaury, is ''less abstract than a university'' and ''more targeted on public policy.''
Thomas Cronin, a specialist on American government at Colorado College and a former fellow at Brookings, agrees. ''Most people on congressional staffs or on the White House staff don't have a lot of time for conceptual thinking,'' he says, ''so these institutes have cropped up as intermediaries between the pure theorists and the pure activists.''
Tait Trussell, vice-president for administration at AEI, explains that the difference in purpose between think tanks and universities produces differing structures. Like most major think tanks, AEI has ''project areas but not departments,'' he says. The projects themselves tend to be interdisciplinary and often involve researchers both inside and outside the institute. Many such think tank projects turn into books: A new study from Brookings titled ''The Painful Prescription: Rationing Hospital Care,'' was written jointly by Henry J. Aaron, a Brookings economist, and William B. Schwarts, a professor of medicine at Tufts University. Some projects, such as AEI's 10-year program on the American Constitution, involve dozens of scholars and millions of dollars. That demand for an interdisciplinary approach - coupled with the changing nature of the problems facing the nation - requires of think tanks a flexibility that universities do not have. Think tanks, for instance, do not normally extend tenure to their staff, who are typically kept on the payroll only as long as they are steadily producing work that meets the organization's standards of quality and immediacy.
Not surprisingly, that lack of tenure raises questions about the independence of the researchers - and about the enormous authority concentrated in the hands of those who head the think tanks. Unlike a university president, who can rarely fire a professor with whose research he or she disagrees, the think tank director can shift personnel fairly readily. As a result, think tanks can take on, more quickly than universities, the stamp of those who head them.
Generally, however, think tanks tend to employ established scholars or public figures and give them a free hand. George Marotta, a senior fellow in foreign affairs at Hoover who also coordinates the institution's public affairs office, says his organization allows fellows to set their own research agenda. ''Our scholars are so senior when they come,'' he says, ''that they just come and continue their own research.'' He adds, ''I've been here 10 years, and not very many people move on.'' AEI, in fact, has several endowed chairs - one funded by the Reader's Digest, and another by the Ford Motor Company.
But the overall direction taken by a think tank's research can be influenced by its source of funding - not as much as in the case of a contract research corporation, perhaps, but more easily than in a university. Many think tanks operate on a mix of funds from foundation gifts, government research grants, endowment income, individual and corporate contributions, sales of books, and fees from seminars. Some, however, trace substantial amounts of funding to single donors with clearly identifiable agendas: Heritage, for example, was started 11 years ago with a $250,000 gift from the conservative Colorado brewer Joseph Coors, who has poured in a similar amount each year since. And some think tanks take up some lines of research in response to specific funding sources: When a consortium of foundations recently approached Brookings with a proposal to fund a study of long-term health care, the institution agreed. ''I'm not sure that this is something that would have come to the top of our agenda,'' says Brookings president MacLaury. But since Brookings has long been working on the economics of health care, he adds,''this seemed to us to be ... a happy marriage.'' In the last decade, however, the funding climate for think tanks has shifted - in part, say insiders, because of an explosion in the numbers of new think tanks. Mr. MacLaury attributes some of that growth to a desire by conservatives to emulate the success Brookings once enjoyed almost exclusively as the nation's predominant (and, in former days, liberal-oriented) policy think tank. He also points to the significant growth of government over the past two decades, as well as to the growth of university programs training public-policy analysts. With government touching ''a larger and larger segment of the population,'' he says, the important task of ''evaluating the performance of government in these new areas'' falls to the think tanks - and naturally invites ''differing perspectives on how that job should be done.''Hoover's George Marotta agrees. Government, he points out, is ''23 percent of GNP (gross national product) now, while at the time the income tax was passed (1913) it was only 1 percent.'' So think tanks are needed, he adds, ''to take a second look at the decisions that are made.''Increasingly, however, think tanks also want to be seen, by the public as well as by potential funders, to be taking a first look - not only commenting on but actively shaping policy by putting their ideas squarely before the public. Several years ago, Brookings hired its first public affairs director, Margaret M. Rhoades, to help get its messages across. Heritage had its own in-house public relations office from the outset. It was conceived as ''part of top management, an integral part of policy,'' says Hugh C. Newton, the foundation's public relations counsel. At the Hoover, says Mr. Marotta, ''I try to encourage the scholars to speed up the process of having their research made public by accepting speaking engagements.'' His goal: to send out ''an idea a day'' from the Hoover. Last year, he notes, ''our op-ed program placed over 300 articles in (newspapers) around the country.''So far, independent think tanks remain an essentially American phenomenon - with some highly visible exceptions, like the International Institute for Strategic Studies in London, the Canadian Institute for International Affairs in Toronto, and the Institut Francais des Relations Internationales in Paris. But American think tanks are increasingly being visited by foreign scholars and public figures interested in exporting the concept. Most observers agree, however, that think tanks depend on democracy. ''They're very democratic,'' says Marotta, ''in the sense that they provide the ability to research public-policy issues and publish findings that will help make democratic society more viable and contribute to better decisions.''At Brookings, Roger Semerad agrees. ''Our role is to enhance decisionmaking,'' he says, adding that ''we just naturally as Americans believe there are answers - in the face of all evidence to the contrary.'' The job of the think tank, he says, is to provide ''an agenda of initiatives'' that ''enriches the conversation.''Most observers agree that the think tanks have done just that - and that the results have been beneficial. ''One of the things we do not want to have happen,'' quips Professor Cronin, ''is the separation of brains and state.''