Unexpected changes, on the contrary, lead to windfall gains or losses for those who are in the right or wrong places at a given time. - George Stigler

Unlike the members of the physical and biological sciences, the economist is asked to explain his work in a manner that is interesting and convincing to a weary listener. Yet there is no reason to believe that the explanation of our economic and social world is inherently simpler than the explanation of our physical world.

Early in my professional life, I found that many areas of economics attracted me. I started working and publishing in price theory by 1938. In 1946, I published an early work on linear programming (The Cost of Subsistence) which solved the problem only approximately; George Dantzig soon presented the exact solution. In the 1940s, I began empirical work on price theory, starting with a test of the kinked oligopoly demand curve theory of rigid prices.

Economic theories are infinitely diverse in their predictive power. Entirely too many have zero predictive power-they are statements of tautologies. Thus the statement that to maximize profits one should operate a firm where marginal revenue equals marginal cost is a mere mathematical statement of the condition for a maximum. The example we gave of search theory is not a tautology because we can identify the factors that influence costs and returns.· Some theories have negative power: they predict the opposite of what happens (and then become useful in the hands of a sophisticated user).