Current Comments” EUGENE GARFIELD INSTITUTE FOR SCIENTIFIC INFORMATIO?W 3501 MARKET ST PHIMDELPHIA, PA 191M

Women in . Part 1. The Productivity Puzzle-J. Scott Long on Why Women Biochemists Publish Less than Men

Number 9 March 1, 1993

Introduction

It is not often that a long-standing con- troversy in science is given prominent at- tention in the public press. But the under- representation of women and minorities in science has recently become a “high pro- file” issue. In a rare two-part commentary on the New York Times Op/Ed page, Shirley M. Tilghman, a Princeton University mo- lecular biologist, described the many cul- tural forces that “retard the rate at which women enter the scientific workforce.” IJ Her solutions are to recruit more women, promote them to senior positions, and re- place tenure with a system of regularly reviewed rolling appointments. She also mentioned the “firestorm” sparked by J. scoff L4Jng Radcliffe President Linda Wilson, who suggested that the male dominated and defined culture of science must change to review of this extensive literature is pro- accommodate more women and minori- vided by Harriet Zuckerman, Andrew W. ties.3,4 Mellon Foundation, New York, in The This recent publicity just shows that the Outer Circle: Women in the Scientific scientific community is struggling with the Community.5 same issues confronting society in general. The reasons and solutions for this are In this case, the equitable participation of too numerous to detail here, and were women, minorities, and others in the pro- briefly discussed previously.d But one as- fession. It is certainly not news to research- pect of this great debate has particulady ers that women are underrepresented by al- interested me—how data on the number of most any measure. In terms of graduate papers and citations are used to examine and doctoral degrees, enrollment, senior fac- differences between women and men in ulty or management posts, salaries, acad- science. Studies covering various fields and emy memberships, and other indicators, pre- different time periods have documented a vious studies have convincingly docu- clear difference—women publish fewer pa- mented that women are unequal partners pers. But the reasons for this have not been in science and engineering. An excellent conclusively established. 248 The Productivity Puzzle: Women 1956-1958 and 1961-1963, and 603 women Publish Less, but Why? who received their doctorates during 1950- 1967. Over a 17-year period, he tracked Many causes for the lower comparative 25,000 papers they published and the num- productivity of women scientists have been ber of citations received. In terms of pro- suggested. An intuitively obvious reason is ductivity, males averaged 26 percent more that women scientists must balance career publications during the first three years, in- demands with family obligations, especially creasing to 66 percent between years three bearing and raising children. But Zucker- and four, and 91 percent by the ninth year. man and Jonathan Cole, Columbia Univer- But the percentage differences thereafter sity, reported that marriage and parenthood declined to 59 percent by the 17th year. do not affect women’s publication rates.T,s These trends result from the steady level of Other reasons, ranging from subtle cultural nonpublishing females and the increase in barriers to blatant sexual discrimination, male nonpublishers. Also, while the aver- have also failed to fully account for the age male’s productivity levels off, females lower productivity of women scientists. maintain and even increase their output over Cole and Zuckerrnan have referred to this time. These data and results are discussed as the “productivity puzzle.”g in detail in the first part of the reprint that As I’ve pointed out previously, the un- follows. derrepresentation of and their lower productivity do not mean they The Impact Enigma: Women Have cannot produce high impact research.b For W]gherImpact, but Why? example, in a study of the 1,000 most-cited scientists from 1965 to 1978, 28 women As will be seen in part 2, similar trends scientists were identified. {’JThe average were found in terms of average citations number of papers per woman was indeed per aufhor. No significant differences were lower—88 versus 121 for all 1,000 authors. observed in the first three career years. Be- Also, their average citations were slightly ginning in year four, mean citations for fe- less—3,650 versus 3,811 for the entire males drop substantially while increasing group. But it is interesting to note that the for males. But at the 10th year, average women’s average impact (citations divided citations for males level off and increase by papers) was substantially higher-41 for females. By year 17, averages for males versus 32 for all 1,000 authors. Keep in and females are nearly identical. Long con- mind that the 1,000 authors represented a cludes, not surprisingly, that these differ- wide range of fields in the life, physical, ences “are fotally the result of differences and chemical . Citation rates can in the numbers of articles.”] IThis confirms vary significantly between different spe- Zuckerman’s earlier finding that “aggregate cialties. differences between men and women in Of course, this is by no means a random numbers of publications account for their sample. Rather, the authors were among a differences in citations.”s (p. 46) very select group, the citation “elite” of Most interesting, in terms of average ci- researchers. But the lower productivity— tations per paper (impact), women fare bet- and higher impact-of women scientists ter than men. Papers by males averaged was documented in a well-designed study seven to nine citations over the 17-year p+ of biochemists by J. Scott Long, Indiana riod and remained fairly stable. But females University, Bloornington.1 I It is being re- averaged between 9 and 13 citations per printed here in two parts. paper, and their impact steadily increased Long’s sample consisted of 556 males from years 10 to 17. By the 17th year, the who earned biochemistry PhD’s during average female’s paper was cited 1.5 times

249 more frequently than the average male’s Society for the Social Studies of Science, paper. Social Research Association, American .Sta- Long speculates on the reasons for this tistical Society, and Psychometric Society. but concludes that more detailed analyses His primary research interests currently fo- are needed to account for the higher impact cus on sex differences in scientific careers of women biochemists. This “impact enig– as well as quantitative analyses and mod- ma,” to coin a phrase, is as intriguing as els in research. the productivity paradox and deserves as much attention by sociologists of science. Conclusion

The second part of Long’s study will be About the Author presented in the March 15 issue of Current J. Scott Long received a bachelor’s de- Con?en@. It examines the effects of col- gree from Juniata College, Huntingdon, laboration—with mentors, colleagues, and Pennsylvania, in 1973. He earned both a spouses-on differences in productivity be- master’s and doctoral degree in sociology tween female and male biochemists. Dif- from Cornell University, Ithaca, New York, ferences in author’s position on the paper’s in 1975 and 1977, respectively. He has been byline are also discussed. In addition, part a faculty member of Washington State Uni- 2 presents detailed longitudinal trends in versity, Pullman, and currently is professor both author and paper impact for women of sociology at Indiana University. and men. The author of more than 30 papers and books, Long is editor of Sociological Me?h- ***** ods and Research and has served on the editorial board of Science and My thanks to Al Welljams-Dorof for his Studies. He is a member of the American help in the preparation of this essay, Sociological Association, American Asso- ciation for the Advancement of Science, G1s1 1993

REFERENCES

1. Tilghman S M. Science vs. the female scientist, New York Times 25 January 1993. p. A 17. 2. ------Science vs. women—a radical solution. New York Times 26 January 1993. p, A23 3. Mervia J. Radcliffe president lambastes competitiveness in research The .$cierrrist6(2):3; 7,20 January 1992. 4. WUstm L. Opinion, The .Scierr(isr6(6): 11, 16 March 1992. 5. Zuckerman H. The careers of men and women scientists: a review of current research. (Zuckerman H, Cole J R & Bruer J T, eds.) The ourer circle: women in [he scierrrtfic community. New York: Norton, 1991. p, 27-56. 6. Garfield E. Why aren’t there more women in science? Currerr( Contents (17):5-12, 26 April 1982. (Reprinted in: Garfield E. Essays of an inforrrrarionscienrisr, Philadelphia: 1S1Press, 1983, Vol. 5. p. 498-505.) 7, Cole J R & Zuckerman H. Marriage, motherhed and research performance in science. .$ci.Amer. 256:119-25, 1987. 8. Cole J R. Fair science: women in rhe scierrrific communiry. New York: Free Press, 1979.336 p. 9, Cole J R & Zuckerman H. The productivity puzzle: persistence and change in patterns of publication on men and wornen scientists. (Maehr M L & Steinkamp M W, eds.) Advances in rnorivarion and achievenrerrr,Greenwich, CT JAI Press, 1984. Vol. 2. p. 217-56. 10. Gartield E. The 1,000 contemporary scientists most-cited 1965-1978. Part 1. The basic list and introduction. Currerrr Contents (41):5-14, 12 October 1981. (Reprinted in: Op. cir., p. 269-78. ) 11. Long J S. Measures of sex differences in scientific productivity. Sot. Forces 7 I: 159-78, 1992,

250 Reprinted with permission from Socia/ Forces71: 159-78, 1992. @‘he Universit y of North Carolina Press.

Measures of Sex Differences in Scient~lc Productivity* J. SCOTT LONG, hdiuna University

Abstract Satisfactory and robust explanations of sex differences in scientific productivity remain elusive. This article provides a multidimensional, longitudinal description of the productivity of male and female biochemists. Several jindings have implications for explaining differences in productivity. Sex differences in the numbers ofpublicarions and citarions increase during the first decade of the career but are reversed later in the career. The lower productivity of females results from their overrepresentation among nonpublishers and their underrepresentation among the extremely productive. Among biochemists who publish, differences cannot be explained by patterns of collaboration, which are nearly identical for males and females, with one exception: females are much more likely to collaborate with a spouse. The smaller number of citations received byfemales results from their fewer publications, not from the quality of their publications. Papers by females on average receive more citations than those by males. These and other findings suggest future directions for research to understand sex differences in scientific productivity,

Explaining the immense variation in the of these explanations has been very suc- productivity of scientists is a major research cessful in accounting for sex differences in objective in the sociology of science. The productivity. Indeed, Cole and Zuckerman sex of a scientist is an important source of (1984) aptly label these sex differences “the variation in scientific productivity. The productivity puzzle.” lesser productivity of females has been es- The premise of this article is that the tablished in dozens of studies covering di- failure to explain sex differences in pro- verse fields, spanning decades, and using a ductivity is partially the result of incom- myriad of measures (see Cole& Zuckerman plete descriptions of what it is that needs to 1984; Fox 1983; Hornig 1987; Long 1987; be explained. Too often studies of sex dif- and Zuckerman 1987 for reviews of this ferences in productivity are based on the literature). Many explanations for sex dif- differences in means of a few indicators of ferences in productivity have been pro- productivity measured at a single time.] The posed. Differences may exist in personal resulting evidence is limited in three im- characteristics such as ability, motivation, portant ways. First, comparisons of means and dedication, or in educational back- mask differences in the distributions of pro- ground. Obligations of family and children ductivity. For example, knowing that the may differentially affect the careers of average male publishes twice as much as males and females. Discrimination may the average female provides no insights on make resources more difficult for females whether these differences are due to a dis- to obtain, which in turn can limit their abil- proportionate number of females having ity to publish. A fifth explanation magni- low productivity, a disproportionate num- fies the effects of other processes. The im- ber of males having extremely high pro- portance of even small differences in levels ductivity, or some combination of these. A of causal variables and subtle forms of dis- given difference in means can be gener- crimination may be enhanced by processes ated by a variety of distributions generated of cumulative advantage and disadvantage by substantively different processes. Sec- (Merton [1968] 1973). Unfortunately, none ond, there is no single measure of produc-

* 1 woufd like to thank Rachel A. Rosen feld, .Lowell L, Hargens, Thomas F. Gieryn, and an anonymous reviewer for their comments on this article. Funding was provided by grant SES-8304029 from the National Science Founoktion. Direct correspondence to the author at Indiana University, Department of Sociology, 744 Ballantine Hall, Bloomington, IN 47405. 251 tivity that is adequate or universally ac- The name of the mentor or dissertation cepted (Fox 1983; Edge 1979). While num- supervisor was found for 98Yc of the ber of publications and citations are the sample, using the DGR, dissertation ab- most commonly used measures, other fac- stracting services, inquiries to the depart- tors such as the number of coauthors and ment and institution of the degree, and mail- author position need to be considered. And ings to cohort members. Information on finally, it is important to understand how collaboration with a mentor was obtained differences change over time. Processes of by searching for the mentor’s name on the cumulative advantage are fundamental to list of authors for each student’s papers. the scientific career (Merton [1968] 1973), Information on 25,000 articles published and such processes operate over time. in refereed journals was coded from Chemi- This article provides a multidimensional, cal Absrrac?s. Citations were coded from longitudinal description of how male and Science Citation Index@ for each of the female biochemists differ in scientific pro- three years following a paper’s publication. ductivity. The questions of interest are, Since there may be sex differences in rates What is the degree of difference in produc- of being the first author, both first- and tivity? Does it vary over time? Is it uni- junior-authored papers were coded. To form across measures of productivity? smooth out yearly variations, productivity Without more complete answers to these measures for a given year were averaged questions, attempts to model the processes over three years, including the year before generating sex differences in productivity and the year after the given year. For fe- are necessarily limited. males particular attention was paid to name changes resulting from marriage and di- Data and Sample vorce. If a name change is not known, a female’s publishing may appear to halt The population is defined as all males who when in fact the publications were missed received Ph.D.’s in biochemistry during the due to name changes.z periods 1956-1958 and 1961-1963 (N=556) Given the possibility of cohort effects and all females who received Ph. D.’s in due to changes in the scientific labor mar- biochemistry from 1950 to 1967 (N=603). ket, the legal and social environment of The larger range of years for females is science resulting from the passage of Title necessary due to the smaller number of fe- VII in 1964, or the nature of research within males receiving Ph.D.’s in biochemistry. biochemistry, comparisons of males and fe- The roster of sample members was obtained males could be misleading if controls are from inquiries to departments of biochem- not introduced for the different years dur- istry and university registrars, checks of ing which degrees were obtained, For this dissertation abstracting services, examina- reason the female sample was split into tion of the American Chemical Society’s three cohorts: the cohort receiving degrees Directory of Graduate Research (DGR), between 1950 and 1955, hereafter the 1950 and a search of commencement rosters. female cohort (N=] 53); the cohort receiv- Complete biographic and bibliographic in- ing degrees between 1956 and 1963, here- formation was coded for approximately after the 1956 female cohort (N=230); and 80% of both males and females (556 males, the cohort with degrees obtained after 1963, 603 females). A significant num~r of those hereafter the 1964 female cohort (N=220). for whom complete information was un- The males who received their degrees be- available appear to be either non-U, S. citi- tween 1956 and 1963 are referred to as the zens who returned to their home country or 1956 male cohort (N=556). Analyses focus persons who left the field of biochemistry. on the 1956 cohorts of males and females, The sample may be thought of as the most since these allow comparisons that are not visible 80% of the Ph.D.’s graduating dur- contaminated by different Ph.D. years. For ing the years sampled. example, it is impossible to determine whether differences between the 1956 co- with males starting with 26% more publi- hort of males and the 1950 cohort of fe- cations. The percent difference jumps to males are sex differences or cohort differ- 66?10between years three and four, a pe- ences. Comparisons among the three female riod roughly corresponding to the end of cohorts are given when significant differ- postdoctoral positions and the start of per- ences are found. manent employment. This result suggests that females are less successful in translat- Results ing their postdoctoral investment into in- creased productivity by means of secure Three dimensions of productivity are used: employment. Percent differences steadily frequency, collaboration, and utilization. build, until males average 917. more pub- While frequency of publication is the most lications by the ninth year. At this point fundamental dimension, it has been criti- the productivity of males levels off, while cized for failing to account for collabora- that of females continues to increase. As a tion or to standardize for quality (Lindsey consequence, the percent differences 1978; Nudelman & Landers 1972; Porter steadily decline, to 5970 by year seventeen. 1977). Collaboration is examined by con- Figure I is significant in two major re- sidering the number of authors of a paper spects. First, while cumulative advantage and the existence of certain types of col- may explain the increasing differences in laboration, for example, collaboration with publications during the first decade, it can- a mentor. Quality of work is notoriously not account for the reversal in the second difficult to operationalize and has gener- decade. Second, the steady increase in the ated substantial debate (cf. Cole & Cole average number of publications for females 1973; Edge 1979). In this article the di- indicates that a substantial proportion of mension of quality is thought of in terms females maintain and enhance their pro- of the impact and utilization of articles. ductivity despite difficulties they may en- Two indicators are used: number of cita- counter. The erosion in percent differences tions and the impact of the journal publish- is all the more significant because it is based ing the article. Finally, these measures are on the entire cohort of females, not just on combined in various ways, such as weight- those who remain active in science. If fe- ing each article by the inverse of the num- males are more likely to drop out of sci- ber of authors. ence, sex differences in levels of publica- tion for active scientists would be even

FREQUENCY OF PUBLICATION smaller. Female scientists in the 1956 co- hort and in the 19t54cohort (data not shown) My strategy for describing sex differences do not appear to be marginalized to the in frequency of publication is to begin with extent that they abandon their research ca- the mean number of publications and to reers. elaborate this description by taking closer Publication levels for the 1950 cohort of looks at the shape of the distribution. Sex females are consistent, with a pattern of differences in publications begin during steady decay in scientific activity. This is graduate school, increase over the first de- shown by the long dashed line in FQure 1. cade of the career, and then slowly decline. The early cohort of females begins with a This information is shown in Figure 1, rise in productivity until the third year, fol- which plots the average yearly number of lowed by a steady decline through [he articles for the 1956 cohorts of males and twenty-fifth year. By the sixteenth year, the females and the 1950 cohort of females. last year for which we have data for males, First, consider males and females from males are nearly three times more produc- the 1956 cohorts. Differences in publica- tive. Differences between the 1950 cohort tion are slight during the first three years, and later cohorts are also found in many of

253 FIGURE 1: Average Number of Articles by Career Year

I , 1 # , I

o) , 4 , 0 ‘02468 10 12 14 16 18 20 22 24 26 career Yew

— MALES [1956-1963] “--- ~FEMALES[1950-1955) ---- FEMALES[1956-19631 the analyses below. Explanations are con- among article counts for males and females sidered in the conclusion. from the 1956 cohorts. The hypothesis that Cole and Zuckerman ( 1984) present the correlation matrices are equal can be twelve years of bibliographic data for a rejected (x*=38.70, df=l 5, p=.001 ), with sample of 263 pairs of male and female correlations for males being on average .11 Ph,D.’s in astronomy, biochemistry, chem- larger. The correlations among measures at istry, earth sciences, mathematics, and phys- adjacent times are the most informative. ics. They found increasing differences with They are smallest between years one and four, reflecting the substantial changes that time but did not uncover a reversal of the can occur as a scientist leaves graduate trend toward increasing differences in pub- school and enters the job market. The cor- lications, perhaps due to their shorter time relations between adjacent years for males series. The new evidence on the reversal of increase until year ten and then gradually differences in productivity suggests the need decline. This period of decline corresponds to examine sex differences over more than to the leveling off in the mean number of the first decade of the career. publications starting at year ten. For fe- males, the correlations start much lower STABIUTV OF PRODUCTIVITY than for males and increase steadily, until the correlation between years thirteen and In addition to having fewer publications seventeen is slightly higher than that for than males, the publication rates for females males. The steady increase in the stability are less stable, a result consistent with find- of publication corresponds to the steady rise ings from Zuckerman and Cole (1975). in the average number of publications for Table 1 presents the correlations over time females as seen in Figure 1. Both increases

254 TABLE 1: Correlations among Article Counts over Time for 1956 Cohorta

Year 1 Year 4 Year 7 Year 10 Year 13 Year 17 Year 1 .412 .386 .381 .313 .316 Year 4 .296 .650 .599 .528 .487 Year 7 .338 .469 .765 .617 .576 Year 10 .210 !351 .577 .709 .651 Yeaz 13 .173 .273 .521 .649 .674 Year 17 .185 .261 .440 .601 .690

“ Males (N-556) above dmgonal; females (N-230) below diagonal, in Mica may be the result of females attaining more expected if the 53% of the females in the stable and adequate working conditions, 1956 cohort who began their careers with postdoctoral fellowships had difficulty ob- THE DISTRIBUTION OF PUBLICA TIONS taining adequate employment at the end of the postdoctoral period. This timing is con- The distribution of publications is highly sistent with the 2.6 years mean duration of skewed. The lower extreme of productivity postdoctoral fellowship for this cohort. is represented by those who do not pub- Third, the leveling of mean publications lish. Lack of publication may represent at for males is due to an increase in the per- least three types of activity: a scientist who cent not publishing beginning in the elev- normally publishes may have a period dur- enth year. Among those who continue to ing which no papers are submitted or ac- publish, the mean productivity steadily in- cepted for publication; a scientist may be creases. And finally, the convergence in actively involved in research but may not mean publications for males and females be in a position where publication is al- results from the increase in nonpublishers lowed or required; or a Ph.D. in science among males and the steady level of may no longer be active in science, for nonpublishers among females. Overall, dif- example, when raising a family or pursu- ferences in publication levels are reduced ing other types of work. Since the measure if only scientists who are actively publish- of nonpubiishers is based on counts over a ing are examined. This finding may ex- three-year period, the definition of nonpub- plain inconsistencies in the literature, since lishers is more likely to reflect a long-term some studies are based on all scientists and lack of research activity than a momentary others are based only on active scientists. fluctuation in a steady flow of publications. The mean is also sensitive to extremely Figure 2 plots the percent of nonpub- productive scientists. Thus, to understand lishing Ph.D.’s over a three-year period, the changing relative productivity of males centered in the given year. This figure clari- and females, it is useful to consider the fies the findings from Figure 1. First, the entire distribution of productivity. Figure 3 lower productivity of the 1950 cohort re- compares the distributions of publications sults from a greater proportion of nonpub- over the first seventeen years of the career, Iishers. Among those who publish, the level using box plots (Cleveland 1985). Box plots of productivity closeiy matches that of the consist of a box in the center with whiskers 1956 female cohort. Second, the sharp di- (i.e., vertical lines with small horizontal vergence in mean publications between lines at the end) at each end. Consider the years three and four for the 1956 cohorts first solid box plot in Figure 3. The hori- results from the jump in female nonpub- zontal line at the end of the top whisker Iishers in year four. This jump would be corresponds to the 95th percentile of the

255 FIGURE 2: Percent of Cohort Members with No Articles by Career Year

:~ 02468 10 12 14 16 18 20 22 24 26

Cares3r Year

— MALES [1956-19631 “- ~- FEMALES(1950-1S551 ---- FEMALES[1956-1963) distribution.j ‘flus, 95% of males average first. In year one, the 25th percentile is O; it 2.0 or less articles per year. The horizontal increases to .33 for years three through nine line at the top of the box, located at 1.0, and then returns to 0, This corresponds to marks the 75th percentile. The horizontal the drop in the percentage of nonpublishers line in the middle of the box is the median, after obtaining a Ph.D. and the subsequent or 50th percentile. To help distinguish the rise in the percent that was shown in Fig- medians for males and females, the medi- ure 2. The median rises from .33 in year ans for females have a small vertical line one to .66 in years three through seven and in the center. The bottom of the box lo- to 1.0 from years nine through eleven, with cates the 25th percentile. The median and a drop to .66 for years thirteen through 25th percentile are usually distinct, although seventeen. The leveling off of the mean in some cases (e.g., females in the third observed in Figure 1 reflects the increasing year) the median and the 25th percentile proportion of scientists averaging less than have the same value and the lines coincide. one article per year. At the same time, the There is no whisker at the bottom of the box spread between the median and the 95th since the 25th and 5th percentiles coincide. percentile and from the 75th to the 95th The small squares and circles indicate percentile increases with time, with a small the means for males and females, respec- reversal in year fifteen. Changes in mean tively. This information corresponds exactly publication result from a dual process in to that in Figure 1. By considering the which the most productive scientists in- change in the quartiles of the distribution, crease their productivity relative to other additional information on how the means scientists, and the proportion of scientists change can be obtained. Consider males with very low productivity increases.

2 s FIGURE 3: Box Plots of Articles by Career Year

I 1 1 I I 1 1 I I

T T ! I I I I i I I I I I I I I T I A I A h )4 II $ ; # II+ -L. ..& 024IL 10 12 18 Career Year 1 — MALES[1956-1963] ---- FEMALESC1956-1963)

For females the 25th percentile in year tile for females stays nearly constant for one is O; it increases to .33 in year three years five through seventeen. and then drops to Ofor the remaining years. The following conclusions can be drawn The median is .33 fora11 years, indicating about the changing ratio of publications for that at least half of the cohort averages .33 males and females. First, the male-to-fe- or less articles per year throughout the first male ratio of medians is larger than the seventeen years of the career, compared to ratio of means, reflecting the lesser pro- .66 and l. Oformales. Themedian is lower ductivity of the least productive half of the for females than formales, but unlike the female cohort compared to the least pro- median for males, it does not drop later in ductive half of the male cohort. Second, the career. The failure of the medians to while the female lower half is iess produc- show the steady increase of the mean re- tive than the male lower half, the produc- flects the influence of high publishers on tivity of the least productive half remains the means. More females than males are constant for females but decreases for low publishers, but their proportion does males. The male lower half is responsible not increase over time. While the median for the leveling off of the means observed is constant, the 75th percentile steadily in- in Figure 1. Third, the most productive sci- creases, from .66inyear one to l.Oin years entists increase their lead over the least pro- three through thirteen and to 1.33 for years ductive through time. If one considers the fifteen through seventeen. As with the mean publications of the most productive males, the spread from the median to the 25% of scientists in each year (figure not 95th percentile increases over time. While shown), their average number of publica- the 95th percentile increases steadily for tions increases more rapidly and steadily females, the difference between the 95th than the average for all cohorts. Finally, percentile for males and the 95th percen- differences in means are determined by both

257 extremes of productivity. A greater pro- of differences in the upper extremes of pro- portion of females have very few publica- ductivity, the current results suggest that tions, and the most productive males ex- differences in the least productive scien- ceed the productivity of the most productive tists may be even more important. females by a factor that is generally larger [Editor’s Note: In part 2, to be pub- than the difference among all cohorts. In lished in the March 15 issue of Currenr short, both tails of the distribution are im- Contenf@, Long discusses the effects of portant for understanding sex differences collaboration on sex differences in produc- in the publication of papers. While tivity, author position in paper bylines, and Zuckerman ( 1987) suggests that sex differ- sex differences in citations per author and ences in productivity are largely the result paper.]

Notes

1.Cole and Zuckerman’s ( 1984) “The Productivity Puzzle” is an important exception to this statement. Indeed, the current article can be viewed as an extension of their article.

2, Several methods were employed to track name changes. The request for a vita asked scientists to list names used for professional work. Articles on the vita were checked for name change. For those not providing such information, the names of atl female biochemists listed in biographical sources were recorded. First names were matched against those of sample members. Matches were compared to determine if it was the same person using a new last name. F1rtally, for females whose flow of papers suddenly ceased, Science Citation Index o was used to find pa~rs that cited the scientist’s earlier work. In some cases the citing papers were written by the same scientist using a new last name. One indication of the impact of name changes is that 11.79’Gof the female scientists who published at least one article used two or more last names for their papers. A larger percentage used variations in how their first, middle, and maiden names were indicated.

3. The top whisker in a box plot normally ends at either the 90th percentile or 1.5 times the distance from the median to the 75th percentile. Given the highly skewed nature of the publication distribution, using the 95th percentile was more informative.

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