AGING AND PRODUCTIVITY AMONG ECONOMISTS

Abstract--Economists' productivity over their careers and as measured by publication in leading journals declines very sharply with age. There is no difference by age in the probability that an article submitted to a leading journal will be accepted. Rates of declining productivity are no greater among the very top publishers than among others, and the probability of acceptance is increasingly related to the author's quality rather than the author's age.

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]

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If productivity losses were less among economists with high early productivity (high Ij,

10), b1 would be negative. In fact, for two of the three indexes the estimated b1 is effectively zero. We cannot reject the hypothesis of a linear relationship between late and early productivity. Only for I3 does it appear that productivity loss is higher for top early producers, and even here the effect is quite small. An economist in the top 10% of this sample at year 10 loses only an additional 0.5 (unweighted) paper compared to an average researcher in this sample at year 10. The very top producers in this elite sample keep on producing high-quality research, but at a slower rate. Those who were not at the top early in their careers slow down as rapidly as the top people, but their slowdown leads them to publish increasingly in lower quality outlets.

Another way of examining heterogeneity is to look at how authors of different quality free in the publication process conditional on their efforts. We obtained data on a random sample of initial submissions to a major general journal during a four-month period in 1991. (Some of the data were initially supplied by the journal's office for use in Hamermesh (19

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4).) Refereeing at this journal is double-blind, so that the chance that referees (though possibly not the editors) were affected by authors' reputations is reduced. The ages of the authors of these 313 papers are measured as of 1993 to account for the probable two-year average lag between the submission of a paper and its publication.

The probits included interaction terms between indicator variables for age and the extent of citations. (Low-cited economists were defined as those with fewer than 10 citations per year, well-cited with at least 10.) As figure 1 clearly shows, acceptance rates for each age group differ sharply by citation status. Comparing authors age 36-50 to those over 50, it is quite clear that the degree of heterogeneity increases with age. This appears to be less true in comparing the oldest to the youngest group, but that inference is due mainly to a very small sample. (Only six authors under age 36, the future superstars of the profession, were well cited.) The general tenor of the combined results from this sample is that the profession signals to less able scholars that their work no longer meets the profession's highest standards, and most of them respond by reducing their submissions to the highest quality journals.

We have followed the careers of economists and measured the demographic characteristics of publishers in leading journals. The evidence seems quite clear that publishing diminishes with age, especially publishing in leading journals, at rates as rapid as in the physical sciences. Indeed, remarkably few older people publish successfully in the scholarly outlets on which the profession places the highest value. As economists age, those w ho were the most productive early in their careers are among the few "survivors" still contributing to scholarship through the leading scholarly outlets.

Whether this relationship is due to natural declines in capacity or decreased incentives to produce is extremely difficult to discern. Unlike athletes, where it is likely that pure physical deterioration causes the reduction in productivity with age, among scholars even the fairly subtle facts that we have uncovered can be marshaled as support for each of these competing hypotheses. Without direct observation on how scholars' use of time changes as they age, we are unlikely to be able to distinguish between explanations of the declining ageproductivity relationship in science.

Blank, Rebecca, "The Effects of Double-Blind versus Single-Blind Reviewing," American Economic Review 81 (Dec. 19

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1), 10411067.