Paul Cezanne died in October 1906 at age of 67. In time he would be generally regarded as most influential painter who had worked in nineteenth century (e.g., Clive Bell, 1982; Clement Greenberg, 1993). Art historians and critics would also agree that his greatest achievement was work he did late in his life: in judgment of historian Meyer Schapiro, for example, the years from 1890 to his death in 1906 are a period of magnificent growth (Meyer Schapiro, 1952; Theodore Reff, 1977; Roger Fry, 1989). In spring of 1907, 25-year-old Pablo Picasso showed a few friends a large new painting that would be given title Les Demoiselles d'Avignon. This would become most important painting of twentieth century, as forerunner of Cubism, the most complete and radical artistic revolution since Renaissance, which Picasso and his friend Georges Braque went on to create in next few years (John Golding, 1988; Galenson, 2001). Picasso would paint for another 66 years, until his death in 1973 at age of 92. During this enormously productive career, he would become by far most celebrated artist of twentieth century. Yet he would never again execute a painting as important as Demoiselles, nor produce another body of work as significant as that he made in years between 1907 and outbreak of World War I. The dramatic contrast between careers of Cezanne and Picasso raises intriguing questions about artists' productivity. Art historians have not systematically addressed question of when in their careers modem artists have typically done their best work, and previous research consequently affords no basis for judging whether it is simply a matter of chance that Cezanne and Picasso made their greatest contributions so close in time, in spite of difference of more than 40 years in their ages. But research by psychologists on ages at which successful practitioners in other disciplines have done their best work is suggestive. Mathematicians, theoretical physicists, and poets typically make their most important contributions at younger ages than do astronomers, biologists, and novelists; psychologists have argued that this is because creative ideations can be produced and elaborated more rapidly in disciplines that deal with abstract conceptual entities than in those whose central ideas are more complex and concrete (Harvey C. Lehman, 1953; Dean Keith Simonton, 1988, 1994). Economists have also identified a number of factors that can change relationship between age and productivity within a given activity (Yoram Ben Porath, 1967; Anne P. Bartel and Nachum Sicherman, 1993, 1995). In view of these results for other disciplines, and potential for change considered by economists, we argue that it was not a matter of chance that Cezanne and Picasso made their greatest contributions at such different ages, but rather that this was a result of process that gave rise to creation and early development of modem painting. Under influence of increased demand for innovation that had prompted beginning of modern painting, new generations of artists made painting an increasingly conceptual activity, in which young practitioners could make important advances. We will use evidence drawn from twentieth-century auction market to examine relationship between artists' ages and value of their paintings for a group of artists, including Cezanne and Picasso, who dominated that early development. This will allow a test of hypothesis that this relationship changed systematically during first century of that art. * Galenson: Department of Economics, University of Chicago, Chicago, IL 60637, and National Bureau of Economic Research; Weinberg: Department of Economics, Ohio State University, Columbus, OH 43210. We thank Gary Becker, Britt Salvesen, Tom Sargent, and two anonymous referees for comments, and Thomas Walker for research assistance.