Supporting Online Material for

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1 Supporting Online Material for The Increasing Dominance of Teams in Production of Knowledge Stefan Wuchty, Benjamin F. Jones, Brian Uzzi* *To whom correspondence should be addressed. This PDF file includes: SOM Text Figs. S1 to S5 Tables S1 to S4 References Published 12 April 2006 on Science Express DOI: /science

2 The Increasing Dominance of Teams in the Production of Knowledge Supplementary Material Stefan Wuchty 1, Benjamin F. Jones 2 and Brian Uzzi 3 1 Northwestern Institute on Complexity (NICO), Northwestern University, Evanston, IL 60208, USA 2 Kellogg School of Management, Northwestern University, Evanston, IL 60208, USA 3 Kellogg School of Management, Northwestern University and the Northwestern Institute on Complexity (NICO), Evanston, IL 60208, USA (Corresponding author). 1

3 Overview These supplementary materials provide detailed assessment of individual subfields and other analyses as cited in the paper. Further Notes: Data Data from the ISI database Web of Science ( were downloaded using software from Thomson Scientific. The data includes all full length research articles and shorter research pieces (letters) as classified by the ISI. This excludes books, book reviews, editorial material, meeting abstracts, and several other types of media. See the ISI website for further information on types of documents. Data for patents were drawn from the United States Patent and Trademark Office, covering all utility patents issued from , as compiled by (S1). The ISI subfield classifications include 171 subfields in the sciences and engineering, 54 subfields in the social sciences, and 27 subfields in the arts and humanities. The US Patent and Trademark data is divided into 36 subfields following (S1). These subfields are listed in Supplementary Table S2. Further Notes: Analysis One may test whether the rise in the number of researchers in a field predicts the rise in average team size by running the following regression: log(team size) it = a + b*log(field size) it + v i + m t + u it, where i indexes the subfield, t indexes the year, v i and m t are fixed effects for subfield and year respectively, and u it is an error term. The results show a statistically significant but small association between the number of researchers and average team size in Science and and Social Sciences, but no effect in Arts and Humanities. In Sciences and, for example, the effect implied that a 100% increase in the subfield size is associated with only a 2% increase in average team size. Given that average field size has increased by 2.6 log points over the time span of the data, while team size has increased by 0.6 log points, expansions of field size can explain only.02 x 2.6 / 0.6 = 9% of the increase in team size. This suggests that rises in manpower may be important to the rise in team size yet, at most, a limited part of a richer, multivariate set of explanations. 2

4 Supplementary Figure S1: Frequency distributions of team sizes in (a) Science &, (b) Social Sciences, (c) Arts & Humanities and (d) Patents. In particular, we obtain these curves in the first and last 5 years that are covered by our data (Science &, from to ; Social Sciences from to ; Arts & Humanities to and Patents, from to ). 3

5 Science & Social Sciences Arts & Humanities Patents Supplementary Figure S2: The growth of teams as an extended version of Figure 1 in the main paper. These plots present s over time in the fraction of papers and patents written in teams (panels a-d) and in mean team size (panels e-h). Each point represents a specific subfield in a specific year. Black lines present the arithmetic mean over all subfields in each year. Subfields for publications are defined by the ISI classification system, with 171 different subfields in Science and, 54 subfields in Social Sciences, and 27 subfields in Arts & Humanities. Patents are categorized in 36 subfields as suggested by (S1). 4

6 Science & Social Sciences Arts & Humanities Teams receive more citations Single authors receive more citations Supplementary Figure S3: In analogy to Figure 2 in the main paper, we show the same results without self-citations. 5

7 first 5 years last 5 years Patents Arts & Humanities frequency Social Sciences Science & ratio of team to single frequencies # citations received Supplementary Figure S4: The decline of the exceptional gifted solo scientist (as an extended version of Figure 3 in the main paper). Pooling all publications and patents within the four research categories, we calculated frequency distributions of citations received in the early period (first 5 years of available data, leftmost column) and late period (last 5 years of available data, center column). We distinguished between 6

8 publications and patents that have been written by single authors (orange bars) and teams (green bars) and calculated separate frequency distributions for each group. The ratio of team and solo frequencies (rightmost panels) is also plotted. A ratio greater than 1 indicates that a team-authored paper had a higher probability of producing the given range of citations than a solo-authored paper. In the early period, solo-authors had a substantial advantage in producing the most highly cited work in both sciences and engineering (c) and social sciences (f). In the contemporary period, this advantage reversed; the percentage of team-authored papers that are highly ranked is now substantially greater than the percentage of solo-authored papers that are highly ranked. For example, in science and engineering in the recent period, the fraction of teamauthored papers that receive 1,000+ citations is 6.3 times higher than the fraction of soloauthored papers that achieve such success (see c). The patterns in arts and humanities and patents (panels i and l) are more consistent over time, with teams consistently more likely to produce the highest impact work. Panels: Sciences and (a , b , c ratio); Social Sciences (d , e , f ratio); Arts and Humanities (g , h , i ratio); Patents (j , k , l ratio). 7

9 first 5 years last 5 years Arts & Humanities Social Sciences frequency Science & ratio of team to single frequencies # citations received Supplementary Figure S5: In analogy to Figure 3 in the main paper and Supplementary Figure S4, we show the same results without self-citations. 8

10 Supplementary Table S1: Major subfields. Description of number of papers, mean team size, fraction of teams, and relative team impact score (RTI) with and without self-citations for the beginning and end periods of our analysis. Science & RTI w self RTI w/o self mean size team % fraction teams % % N papers citations citations ,203, ,877, ,804, ,691, ,388, Mathematics 474, Environmental 442, Material Science 434, Geo Sciences 312, Agriculture 278, Computer Science 249, RTI w self RTI w/o self mean size team % fraction teams % % Social Sciences N papers citations citations % Psychology 384, Economics 130, Political Science 124, Education 100, Law 82, Sociology 61, Anthropology 36, RTI w self RTI w/o self mean size team % fraction teams % % Arts & Humanities N papers citations citations % Literature 184, History 95, Art & Architecture 71, Philosophy 52, Dance & Music 39, Religion 36, Theater, Film, TV & Radio 22, Archaeology 13, RTI w self mean size team % fraction teams % Patents N patents citations % Mechanical 373, Chemical 352, Electrical & Electronics 345, Computers & Comm. 273, Drugs & Medical 151, % 9

11 Supplementary Table S2: For each subfield in Science &, Social Sciences, Arts & Humanities and Patents we present the total number of papers/patents, years covered by the data, as well as mean team sizes, mean fraction of work done in teams and relative impact factors (RTI) in the first and last five years of available data. In addition we provide changing rates of these measures. Science & N papers years covered mean team size fraction teams fields first 5 y. last 5 y. % first 5 y. last 5 y. % first 5 y. last 5 y. % Biochemistry 669, General 529, Surgery 391, Pharmacology 386, , Multidisciplinary 385, , Electrical 356, , Applied 353, Multidisciplinary Sciences 328, Neurosciences 322, Condensed Matter 316, , Multidisciplinary 308, , Physical 293, Material Science, Multidisciplinary 286, Immunology 275, , Organic 269, Cell biology 267, Oncology 258, Plant Sciences 257, Mathematics 256, , Atomic 237, Clinical Neurology 203, , Chemical 197, Cardiac 192, Radiology 188, Environmental Sciences 185, , Analytical 184, Biophysics 183, Endocrinology 178, Veterinery Sciences 169, Research 168, Microbiology 165, Astronomy 162, Physiology 153, Genetics and Heredity 152, Pediatrics 151, Psychiatry 149, RTI 10

12 Mathematics, Applied 146, , Inorganic 145, Food Science 141, Instruments 140, Geosciences, Multidisciplinary 138, Biotechnology 138, Public Health 137, Optics 137, Mechanics 135, Nuclear Science 135, Polymer Science 135, Hematology 133, Pathology 133, Zoology 130, Ecology 119, Obstretics 115, Gastroenterology 112, Vascular Diseaese 108, , Mechanical 104, Ophtalmology 103, Dentistry 97, Toxiocology 96, , Metallurgy 95, Urology 93, Marine 93, , Nuclear 92, , Applied 90, Entomology 90, Infectious Diseases 88, Geochemistry 88, , Multidisciplinary 88, Dermatology 87, , Mathematical 85, Spectroscopy 85, Medicinal 84, Energy 84, Nutrition 83, Agriculture, Dairy and Animal Science 83, Respiratory System 82, Agronomy 78, Chrystallography 78, Biochemical Research Methods 78, Anesthesiology 77,

13 Computer Science, Theory 76, Statistics 75, Orthopedics 71, Coating 67, Water Resources 67, Mathematics, Interdisciplinary 67, Virology 65, , Civil 65, Behavioral Sciences 65, Meterology 64, , Particle 62, Agricultural, Multidisciplinary 62, , Fluid 60, Computer Science, Interdisciplinary Applications 59, Transplantation 59, Otorhinolaryngology 58, Psychology 58, Telecommunications 58, Electrochemistry 57, Accoustics 57, Sports Sciences 56, Theromodynamics 54, Medical Technology 54, Management Science 54, , Software 53, Automation 50, Agricultural, Soil 48, Reproductive 46, , Aerospace 45, , Environmental 44, Oceanography 44, , Biomedical 44, Information Systems 43, Ceramics 42, Hardware 42, Developmental 42, Education 40, Fisheries 39, Parasitology 37, Industrial 37, Critical Care 36, Artificial Intelligence 36, Horticulture 35, Health Care 35,

14 Forestry 34, Nursing 32, , Petroleum 30, Nanoscience 30, Geriatrics 29, Evolutionary 29, Paper and Wood 28, Tropical 28, Rheumatology 28, Mining 28, Mineralogy 26, Biodiversity 22, Allergy 22, Construction 21, Geography, Physical 21, Geology 21, Manufacturing 21, Mycology 19, Limnology 19, Anatomy 17, Emergency 17, Paleontology 17, Remote Sensing 15, Material Science, Characterization and Testing 15, History and Philosophy of Science 14, Rehabilitation 14, Ornithology 13, Microscopy 13, Neuroimaging 13, Medical Informatics 13, , Agricultural 12, Substance Abuse 12, Imaging Science 12, Legal, 11, Composites 11, Textiles 11, Transportation 10, Cybernetics 9, , Geological 8, , Ocean 8, , Marine 8, Agricultural Economics and Policy 7, Biomaterials 7, Andrology 6,

15 Robotics 5, Integrative 4, Medical Ethics 4, Social Sciences mean team size fraction teams relat. team impact N papers years covered fields first 5 y. last 5 y. % first 5 y. last 5 y. % first 5y. last 5 y. % Economics 130, Psychiatry 117, Political Science 100, Multidisciplinary Psychology 93, Law 82, Education and Educational Research 78, Experimental Psychology 67, Psychology, Clinical 65, Business 63, Sociology 61, Public Health 49, Management 46, Psychology, Developmental 43, Psychology, Social 42, Social Sciences, Interdisciplinary 38, Information Science 37, Anthropology 36, Educational Psychology 35, Social Issues 35, International Relations 34, Psychology, Applied 33, Rehabilitation 33, Business, Finance 31, Nursing 30, Environmental Studies 28, Psychology, Biological 27, Geography 26, Planning 25, Applied Linguistics 23, Area Studies 22, Mathematical Social Sciences 21, Education, Special 21, Gerontology 20, Health Policy 20, Social Work 19, Industrial Relations 18, Social Sciences, Biomedical 17,

16 Family Studies 16, Public Administration 16, Criminology and Penology 16, Communication 15, UrbanStudies 13, History and Philosophy of Science 13, Ethics 12, Psychology, Psychoanalysis 11, Ergonomics 11, Demography 11, Substance Abuse 10, Psychology, Mathematical 10, History 9, Womens Studies 9, History of Social Sciences 7, Transportation 5, Ethnic Studies 2, Arts & Humanities mean team size fraction teams relat. team impact N papers years covered fields first 5 y. last 5 y. % first 5 y. last 5 y. % first 5y. last 5 y. % History 84, Multidsciplinary Humanities 62, Literature 60, Philosophy 52, Art 42, Literary Reviews 38, Religion 36, Music 34, Theory of Language and Linguistics 31, Architecture 29, Literature, Romance 28, Archaeology 13, Classics 12, Film, Radio and TV 12, Asian Studies 11, History and Philosophy of Science 10, Theater 10, Literature, German 9, Medieval Studies 8, Literary Theory 7, Literature, british 6, Dance 5, Poetry 4,

17 Literature, Slavic 4, Literature, American 4, Folklore 4, Literature, African, Australian and Canadian 3, Patents mean team size fraction teams relat. team impact N patents years covered fields first 5 y. last 5 y. % first 5 y. last 5 y. % first 5y. last 5 y. % Miscellaneous, Chemical 214, Miscellaneous, Others 179, Materials Processing & Handling 108, Miscellaneous, Mechanical 103, Communications 98, Computer Hardware & Software 83, Motors, Engines & Parts 78, Organic Compounds 78, Drugs 77, Resins 74, Power Systems 73, Electrical Devices 65, Metal Working 63, Surgery & Medical Instruments 62, Measuring & Testing 62, Transportation 61, Miscellaneous, Electrical 52, Optics 51, Semiconductor Devices 47, Agriculture, Husbandry, Food 44, Furniture, House Fixtures 43, Receptacles 43, Information Storage 43, Apparel & Textiles 35, Electrical Lighting 33, Coating 32, Nuclear & X-ray 32, Earth Working & Wells 29, Biotechnology 29, Heating 28, Computer Peripherals 22, Amusement Devices 22, Pipes & Joints 18, Agriculture, Food, Textiles 18, Miscellaneous, Drugs & Medical 14, Gas 10,

18 Supplementary Table S3: In the paper we merge subfields into larger branches of Science &, Social Sciences, Arts & Humanities, and Patents. Here, we show these fields with the subfields they contain. fields Science & sub-fields (according to ISI) ALLERGY ANATOMY & MORPHOLOGY ANDROLOGY ANESTHESIOLOGY BEHAVIORAL SCIENCES CARDIAC & CARDIOVASCULAR SYSTEMS CLINICAL NEUROLOGY CRITICAL CARE MEDICINE DENTISTRY, ORAL SURGERY & MEDICINE DERMATOLOGY EMERGENCY MEDICINE ENDOCRINOLOGY & METABOLISM GASTROENTEROLOGY & HEPATOLOGY GERIATRICS & GERONTOLOGY HEALTH CARE SCIENCES & SERVICES HEMATOLOGY IMMUNOLOGY INFECTIOUS DISEASES INTEGRATIVE & COMPLEMENTARY MEDICINE MEDICAL ETHICS MEDICAL INFORMATICS MEDICAL LABORATORY TECHNOLOGY MEDICINE, GENERAL & INTERNAL MEDICINE, LEGAL MEDICINE, RESEARCH & EXPERIMENTAL NEUROIMAGING NEUROSCIENCES OBSTETRICS & GYNECOLOGY ONCOLOGY OPHTHALMOLOGY ORTHOPEDICS OTORHINOLARYNGOLOGY PATHOLOGY PEDIATRICS PERIPHERAL VASCULAR DISEASE PHARMACOLOGY & PHARMACY PHYSIOLOGY RADIOLOGY, NUCLEAR MEDICINE & MEDICAL IMAGING RESPIRATORY SYSTEM RHEUMATOLOGY SURGERY TOXICOLOGY TRANSPLANTATION TROPICAL MEDICINE UROLOGY & NEPHROLOGY BIOCHEMICAL RESEARCH METHODS BIOCHEMISTRY & MOLECULAR BIOLOGY BIODIVERSITY CONSERVATION BIOLOGY BIOPHYSICS BIOTECHNOLOGY & APPLIED MICROBIOLOGY CELL BIOLOGY DEVELOPMENTAL BIOLOGY 17

19 ENTOMOLOGY EVOLUTIONARY BIOLOGY GENETICS & HEREDITY MARINE & FRESHWATER BIOLOGY MICROBIOLOGY MICROSCOPY MYCOLOGY ORNITHOLOGY PALEONTOLOGY PARASITOLOGY PLANT SCIENCES REPRODUCTIVE BIOLOGY VIROLOGY ZOOLOGY CHEMISTRY, ANALYTICAL CHEMISTRY, APPLIED CHEMISTRY, INORGANIC & NUCLEAR CHEMISTRY, MEDICINAL CHEMISTRY, MULTIDISCIPLINARY CHEMISTRY, ORGANIC CHEMISTRY, PHYSICAL CRYSTALLOGRAPHY ELECTROCHEMISTRY FOOD SCIENCE & TECHNOLOGY POLYMER SCIENCE SPECTROSCOPY ACOUSTICS ASTRONOMY & ASTROPHYSICS NUCLEAR SCIENCE & TECHNOLOGY OPTICS PHYSICS, APPLIED PHYSICS, ATOMIC, MOLECULAR & CHEMICAL PHYSICS, CONDENSED MATTER PHYSICS, FLUIDS & PLASMAS PHYSICS, MATHEMATICAL PHYSICS, MULTIDISCIPLINARY PHYSICS, NUCLEAR PHYSICS, PARTICLES & FIELDS THERMODYNAMICS AUTOMATION & CONTROL SYSTEMS CONSTRUCTION & BUILDING TECHNOLOGY ENERGY & FUELS ENGINEERING, AEROSPACE ENGINEERING, BIOMEDICAL ENGINEERING, CHEMICAL ENGINEERING, CIVIL ENGINEERING, ELECTRICAL & ELECTRONIC ENGINEERING, ENVIRONMENTAL ENGINEERING, GEOLOGICAL ENGINEERING, INDUSTRIAL ENGINEERING, MANUFACTURING ENGINEERING, MARINE ENGINEERING, MECHANICAL ENGINEERING, MULTIDISCIPLINARY ENGINEERING, OCEAN ENGINEERING, PETROLEUM HORTICULTURE IMAGING SCIENCE & PHOTOGRAPHIC TECHNOLOGY INSTRUMENTS & INSTRUMENTATION 18

20 Environmental Environmental Environmental Environmental Environmental Environmental Mathematics Mathematics Mathematics Mathematics Geosciences Geosciences Geosciences Geosciences Geosciences Geosciences Geosciences Computer Computer Computer Computer Computer Computer Computer Agriculture Agriculture Agriculture Agriculture Agriculture Agriculture fields Psychology Psychology Psychology Psychology Psychology Psychology Psychology Psychology Psychology Psychology Economics Political Political Education Education Law Sociology Anthropology MECHANICS METALLURGY & METALLURGICAL ENGINEERING MINING & MINERAL PROCESSING NANOSCIENCE & NANOTECHNOLOGY REMOTE SENSING ROBOTICS TELECOMMUNICATIONS TRANSPORTATION SCIENCE & TECHNOLOGY ECOLOGY ENVIRONMENTAL SCIENCES FISHERIES FORESTRY METEOROLOGY & ATMOSPHERIC SCIENCES WATER RESOURCES MATHEMATICS MATHEMATICS, APPLIED MATHEMATICS, INTERDISCIPLINARY APPLICATIONS STATISTICS & PROBABILITY GEOCHEMISTRY & GEOPHYSICS GEOGRAPHY, PHYSICAL GEOLOGY GEOSCIENCES, MULTIDISCIPLINARY LIMNOLOGY MINERALOGY OCEANOGRAPHY COMPUTER SCIENCE, ARTIFICIAL INTELLIGENCE COMPUTER SCIENCE, CYBERNETICS COMPUTER SCIENCE, HARDWARE & ARCHITECTURE COMPUTER SCIENCE, INFORMATION SYSTEMS COMPUTER SCIENCE, INTERDISCIPLINARY APPLICATIONS COMPUTER SCIENCE, SOFTWARE ENGINEERING COMPUTER SCIENCE, THEORY & METHODS AGRICULTURAL ECONOMICS & POLICY AGRICULTURAL ENGINEERING AGRICULTURE, DAIRY & ANIMAL SCIENCE AGRICULTURE, MULTIDISCIPLINARY AGRICULTURE, SOIL SCIENCE AGRONOMY Social Sciences sub-fields (according to ISI) PSYCHOLOGY, APPLIED PSYCHOLOGY, BIOLOGICAL PSYCHOLOGY, CLINICAL PSYCHOLOGY, DEVELOPMENTAL PSYCHOLOGY, EDUCATIONAL PSYCHOLOGY, EXPERIMENTAL PSYCHOLOGY, MATHEMATICAL PSYCHOLOGY, MULTIDISCIPLINARY PSYCHOLOGY, PSYCHOANALYSIS PSYCHOLOGY, SOCIAL ECONOMICS INTERNATIONAL RELATIONS POLITICAL SCIENCE EDUCATION & EDUCATIONAL RESEARCH EDUCATION, SPECIAL LAW SOCIOLOGY ANTHROPOLOGY 19

21 fields Literature Literature Literature Literature Literature Literature Literature Literature Literature Literature Literature History History Art & Architecture Art & Architecture Philosophy Music & Dance Music & Dance Religion Theater, Film, TV & Radio Theater, Film, TV & Radio Archaeology fields Chemical Chemical Chemical Chemical Chemical Chemical Computers & Communication Computers & Communication Computers & Communication Computers & Communication Drugs & Medical Drugs & Medical Drugs & Medical Drugs & Medical Electrical & Electronics Electrical & Electronics Electrical & Electronics Electrical & Electronics Electrical & Electronics Electrical & Electronics Electrical & Electronics Mechanical Mechanical Mechanical Mechanical Mechanical Mechanical Arts & Humanities sub-fields (according to ISI) LANGUAGE & LINGUISTICS THEORY LITERARY REVIEWS LITERARY THEORY LITERATURE, african, australian & canadian LITERATURE, american LITERATURE, british LITERATURE, german LITERATURE LITERATURE, romance LITERATURE, slavic POETRY HISTORY HISTOR & PHIOLOSOPGY OF SCIENCE ART ARCHITECTURE PHILOSOPHY DANCE MUSIC RELIGION FILM, RADIO, TV THEATER ARCHAEOLOGY Patents sub-fields AGRICULTURE, FOOD, TEXTILES COATING GAS ORGANIC COMPOUNDS RESINS MISCELLANEOUS CHEMICAL COMMUNICATIONS COMPUTER HARDWARE & SOFTWARE COMPUTER PERIPHERALS INFORMATION STORAGE DRUGS SURGERY & MEDICAL INSTRUMENTS BIOTECHNOLOGY MISCELLANEOUS DRUGS & MEDICAL ELECTRICAL DEVICES ELECTRICAL LIGHTING MEASURING & TESTING NUCLEAR & X-RAY POWER SYSTEMS SEMICONDUCTOR DEVICES MISCELLANEOUS ELECTRICAL MATERIALS PROCESS & HANDLING METAL WORKING MOTORS, ENGINES & PARTS OPTICS TRANSPORTATION MISCELLANEOUS MECHANICAL 20

22 Supplementary Table S4: The citation advantage of teams is increasing when we compare teams of any particular size versus solo authors. Each cell reports a ratio, where the numerator is the average number of citations received in that year by a team of size k, and the denominator is the average citations received by teams of size 1. The size of teams used in the numerator is indicated at the top of each column. For example, in Science and, papers with two authors received 1.30 times more citations than solo authors in 1960 but 1.74 times more citations in the 2000, indicating a large increase in the advantage of teamwork. ratios of mean number of received citations year solo team size 2 / solo team size 3 / solo team size 4 / solo team size 5 / solo team size >5 / solo Science & Social Sciences Arts & Humanities Patents

23 References Supplementary Material S1. B.H. Hall, A.B. Jaffe, M. Trajtenberg, National Bureau of Economic Research Working Paper #8498 (2001). 22