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AGING AND PRODUCTIVITY AMONG ECONOMISTS(2)

2013-11-25 01:29 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.

II. Heterogeneity in Declining Productivity

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 I_j, j = 1, 2, 3, we estimate b₀ and b₁ in

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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 that b₀ = 1 and b₁ = 0 (i.e., no productivity loss) is rejected (F-statistics of 134, 152, and 39, respectively). Productivity loss is least severe in I₃, which weights all journals equally, regardless of quality.

If productivity losses were less among economists with high early productivity (high I_j,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 (1994).) 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 simple fact in these additional data is that acceptance rates at this journal are remarkably constant by author's age. The probabilities of an article being accepted are 0.122, 0.114, and 0.123 in the three age groups </=35, 36-50, and >50, respectively.[8] On average there is no decline with age in the acceptance rate of papers submitted to this journal.[9] Probits on the acceptance of a submission that also included variables indicating whether the author was a member of the AEA, was in a top 20 department (as listed in Blank, 1991), was resident in North America, or was female, and the author's prior citation record yield an identical conclusion. The declining presence of older authors in top economics journals does not occur because older authors who keep submitting papers suffer higher rejection rates.

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.

III. Conclusions

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