In this paper I propose a structured approach to specifying social weight matrices that reflect the influence of social networks on individual behavior. I illustrate this approach by applying it to investigating the impact of collaboration and citation networks on the research productivity of academic economists.
My approach proceeds in three steps. First I visualize and report with descriptive statis-tics the important properties of the analyzed networks in order to document that they satisfy the ‘small-world’ properties which implies that they are well-behaved social networks. Second, I rely on two socio-economic theories to identify the circle of influential individuals. These two competing theories of social influence on individual behavior describe the role of commu-nication and comparison. In my illustration I then apply these theories on the community of researchers, arguing that mainly due to the competitive forces prevailing in research, the comparison process is the preferred social driver of research productivity. These first two steps lead me to a benchmark specification of the social weight matrix which is based on the citation network. To quantify proximity between pairs of individuals, I use a measure of structural equivalence.
The third step consists of defining five alternative weight matrices which I obtain in each case by relaxing a specific assumption of the benchmark social weight matrix. I then estimate for each alternative matrix a network autocorrelation model of research productivity.
Afterwards, I apply a Bayesian procedure of model selection to measure the performance of the benchmark matrix as compared to the alternative matrices. In my illustrating example, I find that the benchmark social weight matrix outperforms the alternatives in all but one cases. Moreover, the Bayesian analysis has shown that weight matrices based on the citation network outperform weight matrices based on the collaboration network
My results suggest that the citation network, which represents the sociological process of comparison, is the preferred portrait of interactions among scientists. This result agrees
81
with Burt’s (1987, 2010) view that comparison is the strongest social process in a group of competing individuals.
Even though I use bibliographic data on German academic economists, the proposed approach can readily be applied to researchers in other disciplines and also to other socio-economic contexts in which network effects on individual behavior are to be investigated.
82
Bibliography
Acedo, F. J., C. Barroso, C. Casanueva, and J. L. Gal´an (2006). Co-authorship in management and organizational studies: An empirical and network analysis. Journal of Management Studies 43, 957–983.
Anselin, L. (1988). Spatial Econometrics: Methods and Models. Kluwer: Dordrecht.
Anselin, L. (2010). Thirty Years of Spatial Econometrics. Papers in Regional Science 89(1), 3–25.
Anselin, L. and A. K. Bera (1998). Spatial dependence in linear regression models with an introduction to spatial econometrics. In A. Ullah and D. E. A. Giles (Eds.), Handbook of Applied Economic Statistics, pp. 237–289. New York: Marcel Dekker.
Azoulay, P., J. Zivin, and J. Wang (2010). Superstar extinction. The Quarterly Journal of Economics 125(2), 549–589.
Battisti, M. and G. Di Vaio (2009). A Spatially Filtered Mixture ofβ-Convergence Regressions for EU Regions, 1980-2002. In G. Arbia and B. H. Baltagi (Eds.), Spatial Econometrics.
Methods and Applications, pp. 105–121. Physica Verlag.
Bonaccorsi, A. and C. Daraio (2005). Exploring Size and Agglomeration Effects on Public Research Productivity. Scientometrics 63, 87–120.
Borjas, G. J. and K. B. Doran (2014). Which Peers Matter? The Relative Impacts of Collaborators, Colleagues, and Competitors. NBER Working Paper No. 20026.
Bosquet, C. and P.-P. Combes (2013). Are Academics Who Publish More Also More Cited?
Individual Determinants of Publication and Citation Records. Scientometrics 97, 831–857.
Bourdieu, P. (1975). The Specificity of the Scientific Field and the Social Conditions of the Progress of Reason. Social Science Information 14(1), 19–47.
Bramoull´e, Y., H. Djebbari, and B. Fortin (2009). Identification of peer effects through social networks. Journal of Econometrics 150(1), 41–55.
83
Brandsma, A. S. and R. H. Ketellapper (1979). A biparametric approach to spatial autocor-relation. Environment and Planning A 11(1), 51–58.
Burt, R. S. (1987). Social contagion and innovation: Cohesion versus structural equivalence.
American Journal of Sociology 92, 1287–1335.
Burt, R. S. (2010). Neighbor Networks. Competitive Advantage Local and Personal. Oxford University Press.
Cainelli, G., A. de Felice, M. Lamonarca, and R. Zoboli (2006). The publications of Italian economists in Econlit; Quantitative assessment and implications for research evaluation.
Economia Politica 23(3), 385–424.
Can, A. (1990). The Measurement of Neighborhood Dynamics in Urban House Prices. Eco-nomic Geography 66(3), 254–272.
Carayol, N. (2008). An Economic Theory of Academic Competition: Dynamic Incentives and Endogenous Cumulative Advantages. In M. Albert, S. Voigt, and D. Schmidtchen (Eds.), Scientific Competition. Conferences on New Political Economy, Volume 25, pp. 179–203.
Mohr Siebeck, T¨ubingen.
Carvalho, R. and M. Batty (2006). The Geography of Scientific Productivity: Scaling in U.S.
Computer Science. Journal of Statistical Mechanics 10(1), 1–11.
Coleman, J., E. Katz, and H. Menzel (1966). Medical Innovation. New York: Bobbs-Merrill.
Collins, R. (1998). The Sociology of Philosophies: A Global Theory of Intellectual Change.
Cambridge: Harvard University Press.
Combes, P.-P. and L. Linnemer (2003). Where are the economists who publish? Publication concentration and rankings in Europe based on cumulative publications. Journal of the European Economic Association 1(6), 1250–1308.
Combes, P.-P. and L. Linnemer (2010). Inferring missing citations: A quantitative multi-criteria ranking of all journals in economics. GREQAM DT 2010-25.
Corrado, L. and B. Fingleton (2012). Where is the Economics in Spatial Econometrics?
Journal of Regional Science 52(2), 210–239.
Crane, D. (1972). Invisible Colleges: Diffusion of Knowledge in Scientific Communities. The University of Chicago Press.
Cronin, B., D. Shaw, and K. la Barre (2003). A Cast of Thousands: Coauthorship and Subauthorship Collaboration in the 20th Century as Manifested in the Scholarly Journal Literature of Psychology and Philosophy. Journal of the American Society for Information Science and Technology 54(9), 855–871.
84
Dasgupta, P. and P. A. David (1994). Toward a New Economics of Science.Research Policy 23, 487–521.
de Nooy, W., A. Mrvar, and V. Batagelj (2005). Exploratory Network Analysis with Pajek.
Cambridge University Press.
Deutsche Forschungsgemeinschaft (2009). F¨order-Ranking: Institutionen-Regionen-Netzwerke. http://www.dfg.de/download/pdf/dfg_im_profil/evaluation_
statistik/ranking/ranking_2009/gesamtbericht.pdf. (accessed on 17 February 2014).
Dusansky, R. and C. J. Vernon (1998). Rankings of U.S. Economics Departments. Journal of Economic Perspectives 12(1), 157–170.
Elhorst, J. P. (2010). Applied spatial econometrics: Raising the bar. Spatial Economic Analysis 5(1), 9–28.
Elhorst, J. P. and K. Zigova (2014). Competition in research activity among economic de-partments: Evidence by negative spatial autocorrelation. Geographical Analysis 46(2), 104–125.
Fabel, O., M. Hein, and R. Hofmeister (2008). Research productivity in business economics:
An investigation of austrian, german and swiss universities. German Economic Review 9, 506–531.
Fox, M. F. (1992). Research, Teaching, and Publication Productivity: Mutuality Versus Competition in Academia. Sociology of Education 65(4), 293–305.
Frenken, K., S. Hardeman, and J. Hoekman (2009). Spatial Scientometrics: Towards a Cumulative Research Program. Journal of Informetrics 3(3), 222–232.
Friedkin, N. E. (1990). Social Networks in Structural Equation Models. Social Psychology Quarterly 53(4), 316–328.
Galaskiewicz, J. and R. S. Burt (1991). Interorganization Contagion in Corporate Philan-thropy. Administrative Science Quarterly 36, 88–105.
G´alvez, A., M. Maqueda, M. Mart´ınez-Bueno, and E. Valdivia (2000). Scientific Publication Trends and the Developing World. American Scientist 88(6), 526–533.
Garfield, E. (1963). Science citation index 1961. Science Citation Index, v–xvi.
Gibbons, S. and H. G. Overman (2012). Mostly pointless spatial econometrics. Journal of Regional Science 52(2), 172–191.
85
Goyal, S., M. J. van der Leij, and J. L. Moraga-Gonz´alez (2006). Economics: An emerging small world. Journal of Political Economy 114(2), 403–412.
Griffith, D. A. (1976). Spatial Autocorrelation Problems: Some Preliminary Sketches of a Structural Taxonomy. East Lakes Geographer 11, 59–68.
Griffith, D. A. and G. Arbia (2010). Detecting Negative Spatial Autocorrelation in Georefer-enced Random Variables.International Journal of Geographical Information Science 24(3), 417–437.
Hagstrom, W. O. (1975). The Scientific Community. New York: Basic Books.
Hoekman, J., K. Frenken, and F. van Oort (2009). The Geography of Collaborative Knowledge Production in Europe. Annals of Regional Science 43(3), 721–738.
Homans, G. C. (1961). Social Behavior: Its Elementary Forms. Harcourt: Brace & World, Inc.
Hotelling, H. (1929). Stability in competition. The Economic Journal 39, 41–57.
Hummon, N. and P. Doreian (1989). Connectivity in a Citation Network: the Development of DNA Theory. Social Networks 11, 39–63.
Jacob, B. A. and L. Lefgren (2011). The Impact of Research Grant Funding on Scientific Productivity. Journal of Public Economics 95(9-10), 1168–1177.
Kalaitzidakis, P., T. P. Mamuneas, and T. Stengo (2003). Rankings of Academic Journals and Institutions in Economics.Journal of the European Economic Association 1(6), 1346–1366.
Kelejian, H. H. and I. R. Prucha (1998). A generalized Spatial Two-Stage Least Squares Procedure for Estimating a Spatial Autoregressive Model with Autoregressive Disturbances.
Journal of Real Estate Finance and Economics 17(1), 99–121.
Kim, E. H., A. Morse, and L. Zingales (2009). Are elite universities losing their competitive edge? Journal of Financial Economics 93(3), 353–381.
Krapf, M. (2011). Research evaluation and journal quality weights: Much ado about nothing.
Zeitschrift f¨ur Betriebswirtschaft 81(1), 5–27.
Laband, D. N. and M. J. Piette (1994). The Relative Impacts of Economics Journals: 1970-1990. Journal of Economic Literature 32(2), 640–666.
Laband, D. N. and R. D. Tollison (2000). Intellectual collaboration. Journal of Political Economy 108(3), 632–662.
86
Le Gallo, J., C. M. Ertur, and C. Baumont (2003). A Spatial Econometric Analysis of Convergence across European Regions, 1980-1995. In B. Fingleton (Ed.),European Regional Growth, pp. 99–129. Berlin: Springer.
Lee, L.-F. (2004). Asymptotic Distribution of Quasi-Maximum Likelihood Estimators for Spatial Autoregressive Models. Econometrica 72(6), 1899–1925.
Lee, L.-F. (2007). Identification and estimation of econometric models with group interactions, contextual factors and fixed effects. Journal of Econometrics 140(2), 333–374.
Lee, L.-F., X. Liu, and X. Lin (2010). Specification and estimation of social interaction models with network structures. The Econometrics Journal 13(2), 145–176.
Leenders, R. T. A. J. (2002). Modeling social influence through network autocorrelation:
constructing the weight matrix. Social Networks 24, 21–47.
LeSage, J. P. (1999). The Theory and Practice of Spatial Econometrics.
www.spatial-econometrics.com/html/sbook.pdf.
LeSage, J. P. (2014). Spatial econometric panel data model specification: A bayesian ap-proach. Spatial Statistics 9, 122–145.
LeSage, J. P. and R. K. Pace (2009). Introduction to Spatial Econometrics. Boca Raton:
CRC Press\ Taylor & Francis Group.
Levin, S. G. and P. E. Stephan (1991). Research productivity over the life cycle: Evidence for academic scientists. American Economic Review 81(1), 114–132.
Manski, C. (1993). Identification of endogenous social effects: The reflection problem.Review of Economic Studies 60(3), 531–542.
Marsden, P. V. and N. E. Friedkin (1993). Network Studies of Social Influence. Sociological Methods and Research 22(1), 127–151.
Marsden, P. V. and J. Podolny (1990). Dynamic analysis of network diffusion processes. In J. Weesie and H. Flap (Eds.),Social Networks Through Time. Utrecht: Isor.
Maske, K. L., G. C. Durden, and P. E. Gaynor (2003). Determinants of Scholarly Productivity among Male and Female Economists. Economic Inquiry 41(4), 555–564.
Melin, G. and O. Persson (1996). Studying Research Collaboration Using Co-authorships.
Scientometrics 36(3), 363–377.
Merton, R. K. (1973). The Sociology of Science: Theoretical and Empirical Investigations.
Chicago: University of Chicago Press.
87
Milgram, S. (1967). The Small-World Problem. Psychology Today 1(1), 61–67.
Moffit, R. A. (2001). Policy Interventions, Low-Level Equilibria And Social Interactions. In S. Durlauf and P. Young (Eds.), Social Dynamics. MIT Press.
Moody, J. (2004). The Structure of a Social Science Collaboration Network: Disciplinary Cohesion from 1963 to 1999. American Sociological Review 69, 213–238.
Moulton, B. R. (1990). An Illustration of a Pitfall in Estimating the Effects of Aggregate Variables on Micro Units. Review of Economics and Statistics 72(2), 334–338.
Newman, M. E. J. (2001a). The Structure of Scientific Collaboration Networks. PNAS 98(2), 404–409.
Newman, M. E. J. (2001b). Who is the best connected scientist? A study of scientific coauthorship networks. Physical Review E67(arXiv:cond-mat/0011144v2).
Newman, M. E. J. (2004). Coauthorship Networks and Patterns of Scientific Collaboration.
PNAS 101(S1), 5200–5205.
Paelinck, J. and L. Klaassen (1979). Spatial Econometrics. Farnborough: Saxon House.
Palma de, A., V. Ginsburgh, Y. Y. Papageorgiou, and J.-F. Thisse (1985). The Principle of Minimum Differentiation Holds under Sufficient Heterogeneity. Econometrica 53(4), 767–781.
Price de Solla, D. (1965). Networks of Scientific Papers. The pattern of bibliographic references indicates the nature of the scientific research front. Science 149, 510–515.
Rauber, M. and H. W. Ursprung (2008a). Evaluation of Researchers: A Life Cycle Analysis of German Academic Economists. In M. Albert, S. Voigt, and D. Schmidtchen (Eds.), Scientific Competition. Conferences on New Political Economy, Volume 25, pp. 101–122.
T¨ubingen: Mohr Siebeck.
Rauber, M. and H. W. Ursprung (2008b). Life Cycle and Cohort Productivity in Economic Research: The Case of Germany. German Economic Review 9(4), 431–456.
Ritzberger, K. (2008). A Ranking of Journals in Economics and Related Fields. German Economic Review 9, 402–430.
Sibert, J. (1975). Spatial Autocorrelation and the Optimal Prediction of Assessed Values.
Michigan Geographical Publication#14. Ann Arbor: Department of Geography, University of Michigan.
Smith, T. E. (2009). Estimation Bias in Spatial Models with Strongly Connected Weight Matrices. Geographical Analysis 41(3), 307–332.
88
Stephan, P. E. (1996). The Economics of Science. Journal of Economic Literature 34(3), 1199–1235.
Stephan, P. E. (2010). The Economics of Science. In B. H. Hall and N. Rosenberg (Eds.), Handbook of the Economics of Innovation, Volume 1, pp. 217–273. Amsterdam: North Holland.
Strang, D. and N. B. Tuma (1993). Spatial and temporal heterogeneity in diffusion.American Journal of Sociology 3, 614–639.
Taylor, S. W., B. F. Fender, and K. G. Burke (2006). Unraveling the academic produc-tivity of economists: the opportunity costs of teaching and service. Southern Economic Journal 72(4), 846–859.
Ursprung, H. W. and M. Zimmer (2007). Who is the ‘Platz-Hirsch’ of the German Economics Profession? Journal of Economics and Statistics 227(2), 187–208.
Vinck, D. (2010). The Sociology of Scientific Work. Cheltenham: Edward Elgar.
Waldinger, F. (2011). Peer Effects in Science: Evidence from the Dismissal of Scientists in Nazi Germany. Review of Economic Studies 20, 1–24.
Watts, D. and S. Strogatz (1998). Collective dynamics of ‘small-world’ networks.Nature 393, 440–442.
White, H. D., B. Wellman, and N. Nazer (2004). Does Citation Reflect Social Structure?
Longitudinal Evidence from the ‘Globenet’ Interdisciplinary Research Group. Journal of the American Society for Information Science and Technology 55(2), 111–126.
Xie, Y. and K. A. Shauman (2003). Women in Science. Career Processes and Outcomes.
Harvard University Press.
89
Acknowledgment
My thesis, regardless of my own effort, would not have reached today’s format without the support of many people whom I wholeheartedly thank here.
I am most grateful to my supervisor, Prof. Heinrich W. Ursprung, especially for his free and family-friendly supervision, and for his endless effort to make my writings simple, clear and beautiful. I am also thankful to my coauthor J. Paul Elhorst for mediating me his love for applied spatial econometrics and for his enthusiasm in my research topic.
I thank my husband, especially for keeping the idea of my dissertation alive, whenever it be-came too far and too difficult to reach. Many thanks go to my mother and my mother-in-law for the hours they spent caring for my children, while I could be sure they have a great time.
Finally, I thank a whole generation of student assistants of the Political Economy Chair, namely Simon Heß, Susann Adloff, Sebastian Kopf, Maximilian B¨uhler, and Carl Georg Maier for their help with data cleaning, data processing and literature search.
Dear God thank you for all your blessing which accompanied me on this way.
90