1 the determinants of research productivity: a case study of mexico claudia gonzalez-brambila...
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The Determinants of Research Productivity: A Case Study of Mexico
Claudia Gonzalez-BrambilaCarnegie Mellon University
Advisors: Francisco Veloso and Granger Morgan
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Agenda
Introduction Objective The Data The Model Results Conclusions
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Introduction There is a general consensus that S&T
investments enhance economic growth, health, education and security.
However, there is an increased necessity to assess the impact of S&T programs.
This situation has shaped a culture of evaluation and monitoring in research. Publications and citations are the most
common ways to measure the importance of the contributions of a researcher or an organization.
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Introduction (cont)
Publications play an important role: To get access to financial resources for research To recruit and give raises and promotions to scientists To rank universities’ departments As a channel of communication with industry
However, there are not many studies that explore the determinants of individual and collective research productivity
Implications for university administrators and policy makers
Forecast the expected productivity of faculty Design policies to enhance productivity Parameters to compare researchers across different
areas of knowledge and across countries
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Main Findings of Studies Related to the Determinants of Research Productivity
Age Life cycle with peak between 40 and 50
Gender Women publish between 26 to 91% less than men
Education Graduates from top schools, with RA experience and employed in research universities are more productive. Graduates from Grande Ecoles are more productive
Cohort effect
No evidence
Countries studied United States, France and Israel.
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Objective To explore the determinants of research
productivity using a data base of the most productive researchers in Mexico. Age Gender Areas of Knowledge Cohort Country of PhD Level in SNI Critical Mass Budget
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Importance
This is the most comprehensive study of its kind. Number of researchers Considers all areas of knowledge The first outside the developed world
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Data Base Information on 14,328 researchers
in the SNI from 1991 to 2002. The data are classified in two
categories:1. Characteristics of the researchers:
Age Gender Country where PhD was earned Area and discipline
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Data Base (cont.)
2. SNI variables: Level in the system for each year (or no presence) Budget of Conacyt Total number of researchers in SNI by area and
discipline Total number of publications by SNI researchers by
area and discipline.
The source of publications is the Science Citation Index produced by the ISI.
Publications per year per researcher Citations per 4 years per publication
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Number of publications per SNI researcher by year and area
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1975 1980 1985 1990 1995 2000 2005
Year
Me
an
of p
ub
/ye
ar
All areas
Exact Sc
Biol. & Chem.
Health Sc
Social and Hum.
Biotech & Agric.
Engineering
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The model Publicationsit = F (Xit, Zi, ci, uit)
Zi: Stable across time but not across researchers area, gender, country of PhD, cohort
Xit: varies in both dimensions age, age2, level in SNI, lagged budget, total number of researchers, total
number of publications. ci: individual unobserved effect uit: unobserved effect
Method First step: Negative binomial fixed effect model
To estimate the parameters of Xit Second step: Non linear least square method
To estimate the parameters of Zi
Sample Researchers with at least one publication between 1991-2001.
N=7,793 To adjust for quality, citations per 4 years. Publications between 1991-
1997. N=5,658
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Results - AgeResearch Productivity Over the Life Cycle: All Areas of Knowledge
Age
02
Pu
blicatio
ns p
er Year
20 40 60 80 100
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Results - Age (cont.)
Area of Knowledge
Researchers are productive between: (years old)
Peak of publications per year
The peak of productivity is at age: (years old)
All 29-77 1.5 57
Exact Sc. 34-82 1.6 62
Biol. & Chem. 25-83 2.4 58
Health Sc. 28-78 2 56
Social & Human. 35-72 0.9 58
Agric. & Biotech 33-72 0.8 56
Engineering 32-70 1.2 55
Disciplines
Physics 34-82 1.6 62
Biology 25-82 2.7 58
Materials Eng 29-75 1.5 57
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Comparison with Other Studies (Physics)
Factor Mexico USA (Levin & Stephan)
France (Tuner & Mairesse)
Peak of publications / year
1.6 2 2.9
Decline starts (age)
62 45 52
Women publish (paper on average / year)
-0.16 - -0.9
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Possible Explanations SNI encourages researches to continue publishing
The base salary in Mexico is about one third of what researchers actually receive.
Cannot easily be tested because of the lack of an adequate control sample.
The eldest researchers of a research group tend to appear as coauthors in the publications of their colleagues.
Will be tested in future research. Mexican researchers start and finish their careers
some years later than their colleagues in other countries.
There are no systematic differences between those who got their PhD when they were 30 or younger and those who were above 30.
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Results - Gender Women publish 0.08 papers less
than men on average per year
Area of knowledge Proportion of female (%) Gender difference in scientific productivity (paper per year)
Exact Sc. 15 -0.16
Biology & Chemistry 36 -0.08
Health Sc. 39 -0.24
Social & Humanities 38 0
Agricultural Sc. & Biotech. 22 0
Engineering 12 0.06
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Other Results Cohort effects
Researchers who got their PhD before 1960 are more productive than the latest educated.
The latest educated are more productive than researchers in cohort 1971-1980 and 1981-1990
Country of PhD Researchers who got their PhD in the US or Europe are slightly less
productive but graduate when they are younger. Level in SNI
The big jump in research productivity is seen when researchers change from candidate to level 1.
Critical Mass Small but positive effect in the total number of publications in the
same area of knowledge Little effect of saturation considering the total number of researchers
in the same area of knowledge Budget
Positive relation between the budget of the previous year and publications
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Results for citations The peak of citations per four years is 0.3 and
is reached when researchers are 58 years old; this is only one year older than what was found for publications.
Publications of researchers in level 3 receive more citations than any other level.
the most important difference among levels in the program is seen in researchers in Exact Sc.
Health Sc. receive the largest number of citations per four years.
No important difference in what was found with publications
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Conclusions The effect of age in research productivity is
not very important. The SNI might have enhanced research productivity
until the end of researchers working lives. Significant differences among areas of
knowledge. The design of public policies could respond to these
differences. There is no important gender gap in research
productivity. Potentially cohort effects.
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Questions/comments
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Distribution by Area of Knowledge
Engineering16%
Exact Sc.16%
Biology and Chemistry
17%
Health Sc.10%
Social and Humanities
25%
Agricultural Sc. and Biotechnology
16%
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Mexican Publication in ISI
0
1000
2000
3000
4000
5000
6000
7000
Nu
mb
er
of
Pu
bli
ca
tio
ns
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
Year