英语论文:经济学家的老化与生产力 AGING AND PRODUCTIVITY AMONG ECONOMISTS

two indexes that take journal quality into account, the decline appears to be quite substantial. Between years 9-10 and 14-15 elite economists as a group lose 29 to 32% of their output. From years 9-10 to 19-20 they lose 54 to 60%. In other words, productivity losses are on the order of 5 % per year from the time of peak productivity. However, the losses do not appear to accelerate over these 10 years of the economists' work lives. The loss from year 10 to year 20 is approximately twice that from year 10 to year 15. Another way to study the age-productivity relationship is to examine journals rather than individuals. The first row in each pair of years in table 2 shows the ages of authors of full-length refereed articles in several leading journals (American Economic Review, Journal of Political Economy, and Quarterly Journal of Economics).[5] The median age of authors in the 1980s and 1990s was 36. Scholars over age 50 when their studies are published are a minute fraction of all authors in these journals. Creative economics at the highest levels is mainly for the young. That is as true in the 1990s as it was in the 1960s, although the age distribution of authors does seem to have shifted slightly rightward in the late 1970s. The second row in each pair in table 2 shows the age distributions of random samples of the membership of the American Economic Association in years near those for which the authors' ages were tabulated.[6] The distributions are heavily concentrated between 36 and 50. Decadal variations reflect rapid expansion of American universities in the middle and late 1960s, stagnation in the 1970s and much of the 1980s, and a possible fragmentation of the profession in the 1980s as specialized associations expanded. A substantial percentage of AEA members is over age 50 implying that older economists are greatly underrepresented among authors in major journals relative to their presence among those who view themselves as part of the economics profession.[7] Among the several groups of physical scientists analyzed by Levin and Stephan (1992) the decline of productivity (high-quality publishing) with age was very pronounced. McDowell's (1982) small samples of scholars in a variety of disciplines suggest less rapid declines in productivity with age (in publications unweighted by quality), with the sharpest declines and earliest peaks in the "hard" sciences, and later peaks among English professors and historians. The evidence from our two very different types of samples of economists and economics publishing that account for the quality of publications suggests that, for whatever reason, economics is at least as much a "young person's game" as are the physical sciences. The evidence in section I documents the decline in productivity at the sample means. Information on the age-productivity relationship at the extremes of the sample is interesting in its own right and might help shed some light on the possible causes of the apparent decline in productivity with age. The simplest test compares productivity losses among the top early performers with that of the entire sample of economists at elite institutions. Among the top 10% of early producers the mean values of I1, I2, and I3 at year 20 were 64, 50, and 22%, respectively. These means are quite close to those listed for the entire sample in table 1. Thus on average early promise seems to be sustained in this sample. Of the 12 top researchers on whom we have 20 years of data, five were still among the top dozen producers at year 20. These conclusions are confirmed when we examine the entire sample. For each index Ij, j = 1, 2, 3, we estimate b0 and b1 in Multiple line equation(s) cannot be represented in ASCII text. (1) Table 3 reports the parameter estimates. For all three indexes productivity in year 20 is positively and significantly related to productivity in year 10. There is also substantial productivity loss. The joint hypothesis t