(FORTUNE Magazine) – Poll ten economists on an economic question and you'll get at least ten opinions: That's conventional wisdom. It is also wrong. Economists are not the fractious bunch of equivocators that many people imagine. On many issues -- for example, the net decrease in global wealth caused by trade restrictions -- economists are virtually unanimous; it's noneconomists who keep the battle raging. Even on controversial issues economists' differences are often narrower than most people believe. After 200 years, the oldest social science has sorted out many of the big questions. That surprising message comes through loud and clear in a remarkable work called The New Palgrave: A Dictionary of Economics (Stockton Press). The price (please sit down) is $650. For your money you get four volumes comprising 4,194 pages and treating 1,916 entries. The New Palgrave represents the efforts of more than 900 contributors and three editors -- John Eatwell of Trinity College, Cambridge; Murray Milgate of Harvard; and Peter Newman of Johns Hopkins -- who spent four years assembling it. It weighs 20 pounds. Despite its billing, The New Palgrave is not a dictionary. (The name honors R. H. Inglis Palgrave, an Englishman who published his Dictionary of Political Economy in the 1890s.) It is an encyclopedia full of reasoned -- and often highly technical -- arguments, written by economists who are experts on their subjects. The article on the quantity theory of money (often called monetarism), one of the longest at about 20,000 words, is by Milton Friedman, who won the Nobel Prize partly for his work on that subject. The article on input-output analysis of national economies, the achievement that earned Wassily Leontief his Nobel, is by Leontief. If you need a quick definition of gross national product, consult a textbook; The New Palgrave doesn't even contain an entry on that term. But as a sophisticated guide to the state of economic thinking, this work is unmatched. On one of the most contentious economic issues in the world, the feasibility of central economic planning by government, the consensus among economists is striking. Friedrich von Hayek, who won the Nobel Prize in 1974, claimed that government planners could never successfully replace the free market because they could never know what prices to set for the millions of goods that a large, complex economy produces. When Hayek first elaborated his idea in the 1930s and 1940s, it was a minority viewpoint. Today the majority agree with it. In the entry on socialism, for example, Alec Nove, an expert on the Soviet economy and by no means an adherent of the free market, states, ''No socialist should deny the need for economic calculations. With no price mechanism ((read ''market'')) it is not possible to calculate or compare cost, or to measure the intensity of wants.'' John Kenneth Galbraith -- can it be? -- states that price controls on food in Africa have been a major cause of famine. Even more striking is the admission by socialist economist Robert L. Heilbroner that the free market is necessary for freedom in general. He writes in his entry on capitalism that it is ''a system of social domination'' in which ''all profits depend ultimately on inequality of economic position.'' Capitalists' power, he writes, stems from their ability to withhold their property from the use of society. But in the same article Heilbroner does an about-face. He points out that laborers have the same power to withhold their labor. This property right in their labor, says Heilbroner, spells ''emancipation'' for laborers. He writes, ''The greatest achievements of human liberty thus far attained in organized society have been achieved in certain advanced capitalist societies.'' This consensus on the failures of socialism and on the virtues of the free market cannot be attributed to editorial bias. Eatwell, the lead editor, is an economic adviser to Neil Kinnock, leader of Britain's Labour Party. Co-editor Milgate was Eatwell's student. A SERIOUS OMISSION from the The New Palgrave is any mention of the supply- siders' view that high marginal tax rates on personal income can actually keep tax revenues down. The omission is all the more glaring because of evidence (not cited) from Harvard economist Lawrence B. Lindsey that the cut in the top rates in 1981 increased the taxes paid by the rich. The New Palgrave partially fills this lacuna with what it does say about taxes. It reports a finding by Oxford's J. A. Mirrlees, probably the leading expert on optimal taxation, that a government wishing to redistribute income to the poor should set a top marginal tax rate on personal income of only about 20%. Why so low? Because, he calculates, higher rates reduce by too much the incentive to earn extra taxable income. To be sure, the same entry also reports other economists' findings that marginal tax rates as high as 50% -- counting sales taxes and social security payments as well as federal, state, and local income taxes -- can make sense. Now put this consensus range of 20% to 50% in perspective. Remember that before tax reform, the most extreme supply-side tax bill, introduced by Jack Kemp and Robert Kasten, proposed a top rate of 28%; adding state taxes and Social Security would have yielded a top rate of about 40%. In other words, as far as a lot of economists are concerned, Kemp and Kasten are middle-of-the-roaders. Something I have always loved about economics is how a little clear economic reasoning can lead to surprising conclusions. The New Palgrave is full of examples. For instance, David Friedman (Milton's son), in illustrating how economists analyze the effects of laws, considers a hypothetical law requiring landlords to give tenants three months' notice before evicting them. The conclusion that such a law would benefit tenants is obvious -- and false. Friedman notes that the law would make rental housing more attractive, raising demand. It would also raise landlords' costs of providing rental housing. The net result would be higher rents on more secure housing, frustrating the wishes of tenants who would prefer a lower rent and less security. Another surprising conclusion comes from Harvard economist Thomas Schelling, who explains that a man who smokes regularly, far from draining the nation's resources, benefits society. The grisly reason is that he is likely to die earlier, thus alleviating strain on the Social Security system. IN ADDITION TO ESSAYS on economic terms, policies, and theories, The New Palgrave includes 655 biographies of economists. My favorite is Alan Walters's entry on Milton Friedman. Often an economist chooses a specialty not because he is fascinated by it but because it gives him an excuse to use the analytic tools he has mastered. Not Friedman. Walters, a former economic adviser to Margaret Thatcher, tells how Friedman's characteristic approach was to develop the tools needed to analyze issues that interested him. As a statistician during World War II, for example, Friedman and colleagues figured out that the method being used to test ammunition for defects was wasteful. Rather than testing a given number of bullets, they concluded, the testers should stop as soon as their sampling had established a predetermined level of confidence. Friedman's work became the basis of the statistical technique now called sequential sampling. Having solved the problem, Friedman had no desire to sharpen the theoretical knife further; he moved on to more pressing concerns. MIT's Stanley Fischer, in his entry on Paul Samuelson, writes that at a party given for Samuelson in 1983, fellow economist Franco Modigliani went over to the guest of honor, wagged his finger at him, and said, ''You ((pause)) you have enriched our lives.'' So have the editors of The New Palgrave.