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. (来源：http://www.EnglishCN.com)
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. On average there is no decline with age in the acceptance rate of papers submitted to this journal. 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.
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 who 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.
III. Conclusions II. Heterogeneity in Declining Productivity I. Declining Productivity with Age