Aging and Productivity among Eonomists
文章来源: 文章作者: 发布时间:2008-11-25 06:09 字体: [ ]  进入论坛

Abstract--Economists2' 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.

It is well known that productivity declines with age in a wide range of activities. Lehman (1953) suggests an early peak in productivity in a variety of scientific and artistic3 endeavors, and Diamond (1986) documents the pattern for several scholarly pursuits. Levin and Stephan (1992) provide clear evidence that this decline exists even after careful attempts to account for individual and cohort differences. Fair (1994) finds declines in physical ability among elite4 runners, as does Lydall (1968,pp. 113 passim) in physical abilities of the population generally. In this study we examine productivity declines in our own field. The main new results arise from our use of two different types of information, the equivalent of household and establishment data, to study the stone field over essentially5 the same period of time. Section I discusses the general results on aging and productivity, whereas section II presents evidence of the importance of heterogeneity6.
I. Declining Productivity with Age

Using the American Economic Association (AEA) Directory of Members, we identified tenured economics faculty8 at 17 top research institutions and obtained the years of their Ph.D. degrees.[1] With the citation9 index of the Journal of Economic Literature we replicated10 portions of the curricala vitae of each of the 208 economists currently in the economics departments of those institutions who received Ph.D. degrees between 1959 and 1983.[2]

To measure productivity we construct three indexes, combining papers published in refereed11 journals. Prior research suggests that, at least in terms of salary determination, the returns from nonreferred publications are quite low Sauer (1988), so that we ignore such publications in calculating these measures. I1 weights an article by the journal where it appears based on citations12 to that journal, using values generated by Laband and Piette (1994). This index distinguishes strongly among journals. For example, the Journal of Political Economy has a weight of 59.1, whereas Economic Inquiry13 has a weight of 7.9. In constructing I1 we use the weights associated with the decade in which the articles were published. I2 distinguishes somewhat less among journals by assigning all articles in the nine "core" journals identified by Laband and Piette a value of 1, whereas all other journals are valued at 0.5.[3] Finally, I3 gives all papers a weight of 1. Coauthored articles were given half credit, consistent with Sauer's (1988) findings on the economic returns to coauthorship.[4]

We measure the change in productivity over the life cycle by the percentage change in the number of publications from 9-10 years past the Ph.D. to the periods 14-15 years and then 19-20 years after. For most of the elite economists the base period is equivalent (accounting for publication lags) to the time of tenure7, when one might expect that incentives14 to produce are at a peak. Using two-year publication records at each point reduces the effects of noise in the performance measures. One might argue that still other scientific life-cycle mileposts (e.g., attaining15 a full professorship) should be accounted for too (and to some extent the 14-15-year point does this). But our main purpose is simply to provide detailed16 evidence on the relationship to age, and our data are not sufficient to infer the impact of every possible milepost.

Table 1 contains data on productivity loss by Ph.D. vintage measured by each of the three indexes. If we consider I1 and I2, the 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.#p#分页标题#e#

The second row in each pair in table 2 shows the age distributions of random17 samples of the membership of the American Economic Association in years near those for which the authors' ages were tabulated18.[6] The distributions are heavily concentrated between 36 and 50. Decadal variations reflect rapid expansion of American universities in the middle and late 1960s, stagnation19 in the 1970s and much of the 1980s, and a possible fragmentation of the profession in the 1980s as specialized20 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 analyzed21 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 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 parameter22 estimates. For all three indexes productivity in year 20 is positively23 and significantly related to productivity in year 10. There is also substantial productivity loss. The joint24 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 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 economist1 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 outlets25.

Another way of examining heterogeneity is to look at how authors of different quality free in the publication process conditional26 on their efforts. We obtained data on a random sample of initial submissions28 to a major general journal during a four-month period in 1991. (Some of the data were initially29 supplied by the journal's office for use in Hamermesh (1994).) Refereeing30 at this journal is double-blind, so that the chance that referees31 (though possibly not the editors) were affected32 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 submission27 of a paper and its publication.

The simple fact in these additional data is that acceptance rates at this journal are remarkably33 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 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 rejection34 rates.#p#分页标题#e#

The probits included interaction terms between indicator35 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 tenor36 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 who were the most productive early in their careers are among the few "survivors37" 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 deterioration38 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.

Berger, Mark, and Frank Scott, "Changes in U.S. and Southern Economics Deparment Rankings over Time," Growth and Change 21 (Summer 1990), 21-31.

Blank, Rebecca, "The Effects of Double-Blind versus39 Single-Blind Reviewing," American Economic Review 81 (Dec. 1991), 10411067.

Diamond, Arthur, "The Life-Cycle Research Productivity of Mathemati cians and Scientists," Journal of Gerontology 41 (1986), 520-525.


1 economist AuhzVs     
  • He cast a professional economist's eyes on the problem.他以经济学行家的眼光审视这个问题。
  • He's an economist who thinks he knows all the answers.他是个经济学家,自以为什么都懂。
2 economists 2ba0a36f92d9c37ef31cc751bca1a748     
n.经济学家,经济专家( economist的名词复数 )
  • The sudden rise in share prices has confounded economists. 股价的突然上涨使经济学家大惑不解。
  • Foreign bankers and economists cautiously welcomed the minister's initiative. 外国银行家和经济学家对部长的倡议反应谨慎。 来自《简明英汉词典》
3 artistic IeWyG     
  • The picture on this screen is a good artistic work.这屏风上的画是件很好的艺术品。
  • These artistic handicrafts are very popular with foreign friends.外国朋友很喜欢这些美术工艺品。
4 elite CqzxN     
  • The power elite inside the government is controlling foreign policy.政府内部的一群握有实权的精英控制着对外政策。
  • We have a political elite in this country.我们国家有一群政治精英。
5 essentially nntxw     
  • Really great men are essentially modest.真正的伟人大都很谦虚。
  • She is an essentially selfish person.她本质上是个自私自利的人。
6 heterogeneity YrOzI2     
  • The heterogeneity and uneven development of China's economy are rather advantageous in the war of resistance.中国经济的不统一、不平衡,对于抗日战争反为有利。
  • In heterogeneity is creation of the world.世界产生自异质性。
7 tenure Uqjy2     
  • He remained popular throughout his tenure of the office of mayor.他在担任市长的整个任期内都深得民心。
  • Land tenure is a leading political issue in many parts of the world.土地的保有权在世界很多地区是主要的政治问题。
8 faculty HhkzK     
  • He has a great faculty for learning foreign languages.他有学习外语的天赋。
  • He has the faculty of saying the right thing at the right time.他有在恰当的时候说恰当的话的才智。
9 citation 1qyzo     
  • He had to sign the proposition for the citation.他只好在受奖申请书上签了字。
  • The court could issue a citation and fine Ms. Robbins.法庭可能会发传票,对罗宾斯女士处以罚款。
10 replicated 08069c56938bbf6ddcc01ee2fd848af5     
复制( replicate的过去式和过去分词 ); 重复; 再造; 再生
  • Later outplant the seedlings in a replicated permanent test plantation. 以后苗木出圃栽植成重复的永久性试验林。
  • The phage has replicated and the donor cells have lysed. 噬菌体已复制和给体细胞已发生裂解。
11 refereed 673df248690e0f3ab3b8a3dc8cbd06df     
  • Your focus should be on getting papers published in refereed journals. 首要的就是发表文章,而且是在匿名审稿的杂志上。 来自互联网
  • It was a national judge who refereed the game. 执法这场比赛的是国家裁判。 来自互联网
12 citations f545579a8900192a0b83b831bee7f711     
n.引用( citation的名词复数 );引证;引文;表扬
  • The apt citations and poetic gems have adorned his speeches. 贴切的引语和珠玑般的诗句为他的演说词增添文采。 来自《现代汉英综合大词典》
  • Some dictionary writers use citations to show what words mean. 有些辞典的编纂者用引文作例证以解释词义。 来自辞典例句
13 inquiry nbgzF     
  • Many parents have been pressing for an inquiry into the problem.许多家长迫切要求调查这个问题。
  • The field of inquiry has narrowed down to five persons.调查的范围已经缩小到只剩5个人了。
14 incentives 884481806a10ef3017726acf079e8fa7     
激励某人做某事的事物( incentive的名词复数 ); 刺激; 诱因; 动机
  • tax incentives to encourage savings 鼓励储蓄的税收措施
  • Furthermore, subsidies provide incentives only for investments in equipment. 更有甚者,提供津贴仅是为鼓励增添设备的投资。 来自英汉非文学 - 环境法 - 环境法
15 attaining da8a99bbb342bc514279651bdbe731cc     
(通常经过努力)实现( attain的现在分词 ); 达到; 获得; 达到(某年龄、水平、状况)
  • Jim is halfway to attaining his pilot's licence. 吉姆就快要拿到飞行员执照了。
  • By that time she was attaining to fifty. 那时她已快到五十岁了。
16 detailed xuNzms     
  • He had made a detailed study of the terrain.他对地形作了缜密的研究。
  • A detailed list of our publications is available on request.我们的出版物有一份详细的目录备索。
17 random HT9xd     
  • The list is arranged in a random order.名单排列不分先后。
  • On random inspection the meat was found to be bad.经抽查,发现肉变质了。
18 tabulated cb52faa26d48a2b1eb53a125f5fad3c3     
把(数字、事实)列成表( tabulate的过去式和过去分词 )
  • Results for the test program haven't been tabulated. 试验的结果还没有制成表格。
  • A large number of substances were investigated and the relevant properties tabulated. 已经研究了多种物质,并将有关性质列成了表。
19 stagnation suVwt     
n. 停滞
  • Poor economic policies led to a long period of stagnation and decline. 糟糕的经济政策道致了长时间的经济萧条和下滑。
  • Motion is absolute while stagnation is relative. 运动是绝对的,而静止是相对的。
20 specialized Chuzwe     
  • There are many specialized agencies in the United Nations.联合国有许多专门机构。
  • These tools are very specialized.这些是专用工具。
21 analyzed 483f1acae53789fbee273a644fdcda80     
v.分析( analyze的过去式和过去分词 );分解;解释;对…进行心理分析
  • The doctors analyzed the blood sample for anemia. 医生们分析了贫血的血样。 来自《简明英汉词典》
  • The young man did not analyze the process of his captivation and enrapturement, for love to him was a mystery and could not be analyzed. 这年轻人没有分析自己蛊惑著迷的过程,因为对他来说,爱是个不可分析的迷。 来自《简明英汉词典》
22 parameter eK4xZ     
  • It is the parameter of distribution.这就是分布参数。
  • One parameter which always comes into play is the national economy.国民经济是一个经常起作用的参量。
23 positively vPTxw     
  • She was positively glowing with happiness.她满脸幸福。
  • The weather was positively poisonous.这天气着实讨厌。
24 joint m3lx4     
  • I had a bad fall,which put my shoulder out of joint.我重重地摔了一跤,肩膀脫臼了。
  • We wrote a letter in joint names.我们联名写了封信。
25 outlets a899f2669c499f26df428cf3d18a06c3     
n.出口( outlet的名词复数 );经销店;插座;廉价经销店
  • The dumping of foreign cotton blocked outlets for locally grown cotton. 外国棉花的倾销阻滞了当地生产的棉花的销路。 来自《简明英汉词典》
  • They must find outlets for their products. 他们必须为自己的产品寻找出路。 来自《现代汉英综合大词典》
26 conditional BYvyn     
  • My agreement is conditional on your help.你肯帮助我才同意。
  • There are two forms of most-favored-nation treatment:conditional and unconditional.最惠国待遇有两种形式:有条件的和无条件的。
27 submission lUVzr     
  • The defeated general showed his submission by giving up his sword.战败将军缴剑表示投降。
  • No enemy can frighten us into submission.任何敌人的恐吓都不能使我们屈服。
28 submissions 073d6f2167f8d9a96d86b9fe6b9d5b37     
n.提交( submission的名词复数 );屈从;归顺;向法官或陪审团提出的意见或论据
  • The deadline for submissions to the competition will be Easter 1994. 递交参赛申请的截止时间为1994年的复活节。 来自辞典例句
  • Section 556(d) allows the agency to substitute written submissions for oral direct testimony in rulemaking. 第五百五十六条第(四)款准允行政机关在规则制定中用书面提交材料替代口头的直接证言。 来自英汉非文学 - 行政法
29 initially 273xZ     
  • The ban was initially opposed by the US.这一禁令首先遭到美国的反对。
  • Feathers initially developed from insect scales.羽毛最初由昆虫的翅瓣演化而来。
30 refereeing 9ee7651f1cf61af6885190dbe5d22fae     
  • I've spent too much time in my career refereeing staff/line disputes. 办事人员和第一线人员常常发生争执,我为解决这种争执花费了许多时间。 来自辞典例句
  • Unfair refereeing in yesterday's match made the news again. 昨天的比赛中又爆出了“黑哨”丑闻! 来自互联网
31 referees 7891e30f2b42e2d37914dc1ab29ba489     
n.裁判员( referee的名词复数 );证明人;公断人;(专业性强的文章的)审阅人
  • The fiery player has had numerous run-ins with referees. 这位脾气暴躁的队员曾和裁判员发生过无数次争吵。
  • If you want to appeal, the Court of Referees will decide. 如果你要上诉,可以由仲裁法庭去判决。 来自辞典例句
32 affected TzUzg0     
  • She showed an affected interest in our subject.她假装对我们的课题感到兴趣。
  • His manners are affected.他的态度不自然。
33 remarkably EkPzTW     
  • I thought she was remarkably restrained in the circumstances. 我认为她在那种情况下非常克制。
  • He made a remarkably swift recovery. 他康复得相当快。
34 rejection FVpxp     
  • He decided not to approach her for fear of rejection.他因怕遭拒绝决定不再去找她。
  • The rejection plunged her into the dark depths of despair.遭到拒绝使她陷入了绝望的深渊。
35 indicator i8NxM     
  • Gold prices are often seen as an indicator of inflation.黃金价格常常被看作是通货膨胀的指标。
  • His left-hand indicator is flashing.他左手边的转向灯正在闪亮。
36 tenor LIxza     
  • The tenor of his speech was that war would come.他讲话的大意是战争将要发生。
  • The four parts in singing are soprano,alto,tenor and bass.唱歌的四个声部是女高音、女低音、男高音和男低音。
37 survivors 02ddbdca4c6dba0b46d9d823ed2b4b62     
幸存者,残存者,生还者( survivor的名词复数 )
  • The survivors were adrift in a lifeboat for six days. 幸存者在救生艇上漂流了六天。
  • survivors clinging to a raft 紧紧抓住救生筏的幸存者
38 deterioration yvvxj     
  • Mental and physical deterioration both occur naturally with age. 随着年龄的增长,心智和体力自然衰退。
  • The car's bodywork was already showing signs of deterioration. 这辆车的车身已经显示出了劣化迹象。
39 versus wi7wU     
  • The big match tonight is England versus Spain.今晚的大赛是英格兰对西班牙。
  • The most exciting game was Harvard versus Yale.最富紧张刺激的球赛是哈佛队对耶鲁队。