by Baylor University. Barbara Cornelius Hans Landström Olle Persson

Transcription

1 by Baylor University E T& P Entrepreneurial Studies: The Dynamic Research Front of a Developing Social Science Barbara Cornelius Hans Landström Olle Persson Entrepreneurship research has been built upon a historical foundation grounded in economic change. To understand the development of the field, it is useful to understand the motivations and interests of key scholars and to trace the linkages between these scholars and other authors, from the transient to the contributor. This has been done through a bibliometric analysis of research articles cited between 1982 and Entrepreneurship has developed from a subdiscipline of management studies reliant on alien terms and cognitive methods toward a separate field with increasing complexities of its own. While not fully mature, entrepreneurship shows all the signs of a maturing field from its increasingly internal orientation and the establishment of key areas of research through to an enhanced, discipline-specific, theoretical approach with a professional language of its own. Introduction The Emerging Field of Entrepreneurship Research Entrepreneurship is a relatively new field of research that has gained extensive interest beyond the usual areas of management studies during the last few decades. In the 1970s and 1980s, we experienced huge structural changes in society worldwide, e.g., oil crises, economic recessions, technical progress, an increasing internationalization of economies, and far-reaching political changes emphasizing stronger market-oriented ideologies. These changes created a level of uncertainty and disequilibrium that constituted a breeding ground for innovation and entrepreneurship. It was in this context that the interest in entrepreneurship research grew. Thus, the field of entrepreneurship, as a disciplinary research field, is not more than 25 years old, but has developed substantially over that short period of time. Many scientific theorists have discussed how new academic fields are created and how they develop. Focusing on the cognitive aspects of this development, Hansson (1993) Please send correspondence to: Barbara Cornelius, Department of Business Administration, Umeȧ School of Business, S Umeȧ, Sweden; phone: ; fax: ; Barbara. Cornelius@fek.umu.se. May,

2 found two approaches to knowledge creation, the technical and the theoretical. Young fields of research, he suggests, are characterized by a technical approach, the researchers focusing their attention on the object of study (as opposed to theories and methodologies) in a search for knowledge that can be applied in a practical situation. Much of the research is empirical; the aim is primarily to achieve a broad understanding of the study object. However, due to the lack of a conceptual platform, the knowledge is rather fragmented. According to Hansson, mature fields, on the other hand, display a strong theoretical approach to knowledge where immediate applicability is of less importance. This research is often speculative; similar to basic research in the sciences, the aim is to generate new understandings through theoretical musing and the testing of hypotheses. The aim in mature disciplines is to understand, explain, and even predict the future response of the object of study rather than to simply describe it. Following the reasoning of Hansson, entrepreneurship research has applied a technical approach to knowledge generation for many years, describing the phenomenon of entrepreneurship and utilizing a strongly empirical approach. However, the research focus shifted, over time, from areas such as the determination of the psychological characteristics of entrepreneurs toward an assessment of the behavioral and cognitive aspects of the entrepreneur with an increased emphasis on context and on the entrepreneurial process. The quality of the empirical research in entrepreneurship has improved (Chandler & Lyon, 2001), and some researchers have introduced theoretical perspectives, such as the evolutionary approach or the resource-based view, to further their understanding of the discipline (Davidsson, Low, & Wright, 2001). Thus, we believe that the current state of entrepreneurship research is somewhere between the technical or applied, and the theoretical or mature approach to knowledge development. If the field is moving toward maturity, knowledge accumulation should reflect an increasing internal orientation with researchers citing the work of other entrepreneurship researchers; a stabilization of topics within the field, i.e., some topics will crystallize as key questions; an identifiable research community led by core researchers that have been highly influential in the discipline s development; and an increased level of specialization among groups of researchers focused more narrowly on particular theoretical research issues. The Aims and Characteristics of the Study In emerging phases of new research fields, some individuals seem more important than others. These are the researchers who ask the interesting and important questions, and who attract other researchers to the field. These researchers seem to play a major role in giving direction to an emerging field of research as well as in influencing the selection of research problems (Crane, 1972). The emerging field [is] shaped by those who produce research that interests and attracts others to build on their work (Aldrich & Baker, 1997, p. 398). In order to determine the stage of maturation of the field of entrepreneurship, we examine the research output of those key researchers in the field over the past 20 years. We assess the rise and fall of different research themes over time, and have determined whether researchers have provided the foundation for systematic disciplinary advance. That is, we examine the key researchers cited by others to assess whether entrepreneurship scholars accumulate knowledge by building on previous research and by developing a 376 ENTREPRENEURSHIP THEORY and PRACTICE

3 greater depth of understanding, or whether they are, instead, opportunistic followers of trends from other disciplines. We used bibliometric data from the Social Science Citation Indexto determine the development of entrepreneurship research. The approach is not unique and has been applied previously in assessing the interests of entrepreneurship researchers (see, e.g., recent studies by Landström, 2001; Reader & Watkins, 2001; Schildt & Sillanpää, 2004; Watkins & Reader, 2003). The analysis in this article follows from the work of those previously mentioned, but takes a more evolutionary perspective. As in the work of Ramos-Rodrigues and Ruis-Navarro (2004), who examined the intellectual structure of strategic management research, we have taken snapshots of the research profile of key entrepreneurship researchers at different points of time. We focus our analysis on the research front in the field of entrepreneurship. We argue that the development of entrepreneurship research has followed a traditional pattern from exploratory and fragmented studies that allowed researchers to create a generalized understanding of the phenomena toward a more theoretical approach that tests our understanding against predicted responses to given internal and external stimuli. The following section describes our method for collecting the data used and our approach to its analysis prior to presenting an overview of the historical evolution of entrepreneurship as a research field. In three sections, we present our data on the periods examined ( , , and ), discussing both key researchers and more transient research contributions before providing an analysis of the changes that have occurred in entrepreneurship research over the entire period studied. Finally, we summarize what we have learned about the impact of key researchers and their followers on the development of entrepreneurship research. Methods Data Collection We began our data collection by downloading all citations from the Social Sciences Citation Index for refereed academic articles that included the word entrep* in the title, key words, or abstract between 1986 and February, This gave us a total of 4,003 articles but, given that the 2005 period was so incomplete, 52 articles from 2005 were dropped, leaving us with a database of 3,951 articles. These articles make 151,560 references to all kinds of literature with only 65,565 of the references going to the journal publications. Thus, while the Social Sciences Citation Index has historically excluded many of the journals that published entrepreneurial research in the early stages, references to these articles are included from the citing side of the database. Graphing those articles that are cited in entrepreneurship literature against those that are citing the literature gives us a triangular block of increasing size starting from the first articles cited in the beginning of research in the field and growing toward a large number of cited articles. Those that are cited over and over again would provide the foundation line of research work, running along the horizontal axis as shown in Figure 1. We would anticipate that many of these would drop out of usage as continued refinement of concepts made them less relevant than their successors. The research front, by contrast, would be made up of those articles along the diagonal. As our interest is in determining not only those who were important contributors to research in entrepreneurship but in identifying the development of this field of academic endeavor, we have chosen to focus our efforts on this diagonal. May,

4 Figure 1 Determining the Research Front Cited years Research front 1982 Foundation papers 1986 Citing years 2004 Figure 2 Dynamics of Entrepreneurship Research Front Figure 2 shows the sum of citations in each year (vertical axis) against the number of citations (horizontal axis). Those articles included in the highlighted section again represent the research front. To capture the dynamics of this research front, we have chosen to use a 5-year citing window, each year containing the citations from the previous 5 years. That is, a focus on the 5-year period between 1986 and 1990 actually captures material cited back to Similarly, the focus on the period between 1993 and 1997 carries us back to Finally, the 5-year period between 2000 and the end of 2004 includes articles that were in the moving window for 2000 that go back to Our examination of citations is thus limited to the overlapping rectangles shown on the diagram in Figure 2. Through this approach, we will be able to ascertain active researchers in each period, weeding out transient articles and authors. The median age of cited references is 8 years 378 ENTREPRENEURSHIP THEORY and PRACTICE

5 (50% of the citations go to literature that is less than 9 years old), and using the moving citation window, we captured 37% of all citations. Analysis of Data A co-citation analysis of the most cited first authors in a cited reference was undertaken with all pairs arranged in a co-citation matrix. This was then submitted to a multidimensional scaling (MDS) program that made a two-dimensional representation of the co-citation matrix. The resulting coordinates formed the basis for drawing maps demonstrating the relationship between authors. On the maps, the closer two authors are, the more often they are co-cited. The circle area is proportional to the number of citations they received. To be included in the maps derived from the first window ( ), each author had to be cited a minimum of five times in five different articles. To be included in the second window ( ), a period where more authors were actively working in the field of entrepreneurship than in the first, we limited the analysis to those who were cited a minimum of 11 times. Finally, to be included in the final group ( ), each author had to be cited at least 20 times in 20 separate articles. These maps are subsequently presented along with an analysis of their content. Applying a bibliometric approach to the literature cited in each period provides us with information on the interests and aspirations of academic researchers in entrepreneurship during that window in time. We wish to sort out the research that has been undertaken and to determine what complementarities and differences exist, whether there are trajectories in the research and, if so, what these trajectories may be. The bibliometric approach is based upon an assumption that research is undertaken to create a knowledge base that is then published in the interests of other stakeholders (Okubo & Sjöberg, 2000). If authors co-occur in the reference lists, being co-cited, it means that they are intellectually related in some way. Thus, what is cited gives us access to the knowledge base of the field, and the citing articles provide us with information on the research front in each period. Strength and Weaknesses of the Study Entrepreneurship is a multidisciplinary field of research, attracting authors with different backgrounds and different theoretical frameworks, and different levels of analyses and methodological traditions. By using the Web of Science database on citations, we have included those authors who have been published in the primary recognized journals but also those who have been cited by these authors. Thus, those writing in more specialized journals or presenting at academic conferences have been included in our study. A cutoff for inclusion in our key periods was not constant but varied according to the number of authors that would be examined in each. This means that apparently strong and contributing authors in an early period would drop from our analysis in a following period despite their early contribution to the literature. While we have proffered some explanations for this and considered it a probable strength in our analysis, given the growing number of citations in the field over the time studied, the fact remains that some core authors may be ignored. The comprehensive nature of our study, despite the large numbers included, can be questioned. Our authors are, to some extent, self-selected. That is, they had to include entrep* in the title, as a keyword or in the abstract. As a result, authors contributing to the debate that do not use this key word, e.g., those studying self-employment or venture May,

6 capital are not all included herein. Additionally, given the multidisciplinary nature of much of this research, various authors may use the concept of entrepreneurship differently, a problem that is not just one of semantics, as studies of small business have shown. The Evolution of Entrepreneurship as a Research Field Despite its relatively recent ascent to acceptance as an academic field, entrepreneurship research has a long tradition (Landström, 2005, 2000, 1999). Although the term entrepreneur has been used in the French language since the twelfth century, the feudal system operating in the European world at the time hampered the development of entrepreneurship and innovation. Gradually, during the Middle Ages, the situation changed, especially in countries like Italy, France, and Southern Germany, which became the driving forces behind European economic development. Emerging cities created a breeding ground for entrepreneurship, especially among the merchant class who advanced raw material and marketed the finished goods. By the eighteenth century, feudalism was eliminated; legal and institutional conditions had greatly changed with the burgeoning of the joint stock company and the development of a banking system (Wennekers & Thurik, 2001, 1999). Entrepreneurship and innovation thrived. It was the writings of the Irish-born banker, Richard Cantillon (circa ), whose work Essai Sur la Nature du Commerce en Général (1755/1931), published posthumously in 1755, that gave the concept of entrepreneurship an economic meaning and the entrepreneur a role in economic development. However, for a long period of time, classical economic theory, originating in Adam Smith s well-known work Inquiry into the Nature and Causes of the Wealth of Nations (1776/1976), dominated the intellectual development of economic science an economic theory that did not emphasize the entrepreneurial function in the economy. Only a few economists were successful in breaking that trend, and authors like Jean-Baptiste Say ( ), Jeremy Bentham ( ), and John Stuart Mill ( ) should be mentioned in this respect. At the end of the nineteenth century, the European discussion of entrepreneurship found an audience in the United States, which, by that time, was well on the way to becoming a major industrial power. Some of the American economists who developed the discussion about entrepreneurship during this period were Francis Walker, Fredrick Hawley, and John Bates Clark. Perhaps the best-known author among the U.S. economists was Frank Knight ( ), who, in his thesis Risk, Uncertainty and Profit (1921) makes a distinction between risk and uncertainty, where uncertainty is unique and uninsurable, and argues that the skills of the entrepreneur lie in the ability to handle the uncertainty that exists in any given society. The late nineteenth and early twentieth centuries were characterized by the emergence of an industrial society, and it was against this background that the thoughts of Joseph Schumpeter ( ) were developed. Schumpeter s seminal work was Theorie der Wirtschaftlichen Entwicklung (1912, and a rather different second edition was published in 1926) or Theory of Economic Development (1934), which is the English translation of the second edition. In this book, Schumpeter tried to develop an entirely new economic theory based on change as opposed to equilibrium. In chapter 2 of the book, he discusses the function of the entrepreneur as an individual who tends to break the market s equilibrium by introducing innovations into the system. This ability to break with established practice was primarily related to individual entrepreneurs entrepreneurs that were characterized by the desire and the will to found private kingdoms, the will to conquer, and the 380 ENTREPRENEURSHIP THEORY and PRACTICE

7 joy of creating. However, as large corporations increasingly dominated industrial society, Schumpeter s view of entrepreneurship gradually changed from entrepreneurship as the achievement of a single individual to also include innovative activities in existing organizations (Schumpeter, 1942). Schumpeter s reasoning has remained a basic point of reference for many of his successors, both for those who follow his tradition of regarding the entrepreneur as an innovative path breaker (e.g., Baumol, 1968, 1990; Dahmén, 1950; Leibenstein, 1968) and those economists who put forward alternative interpretations of the entrepreneur (e.g., members of the Austrian School represented by von Hayek, von Mises, and more recently, Kirzner [1973]). Despite this background, entrepreneurship continued to be largely overlooked in economic science models models often based on a strong equilibrium paradigm. It was left to behavioral science researchers to continue theoretical development in entrepreneurship research. David McClelland ( ) was one of the first to present empirical studies in the field of entrepreneurship that were based on behavioral science theory. In his pioneering work The Achieving Society (1961), McClelland discussed the question: Why are certain societies more dynamic than others? For McClelland, the premise was that the norms and values that prevail in any given society, particularly with regard to the need for achievement (nach), are of vital importance for the development of that society. By means of a large number of experimentally constructed studies, McClelland showed the link between a country s nach and its economic development. He concluded that countries that are economically more developed are characterized by a stronger focus on institutional norms and openness toward other people and their values, as well as communication between people. It is in this context that entrepreneurs have been recognized as an important driving force for development. Entrepreneurs are people who have a high nach coupled with strong self-confidence and independent problem solving skills, and who prefer situations that are characterized by moderate risk, while accepting individual responsibility. Other researchers displaying an interest in entrepreneurs, from outside the economic disciplines in the 1960s and 1970s, included sociologists like Lipset (1967) and social anthropologists like Geertz (1963) and Barth (1963). It was in the mid-1970s that the world economy first began to show signs that large systems were not always superior in promoting technological development. The twin oil crises triggered an appraisal of the role of small firms. Many large companies were hit by severe economic difficulties, and unemployment became a major problem in many Western societies. Large companies were increasingly seen as inflexible and slow to adjust to new market conditions. Carlsson (1992) found two explanations for a greater interest in smaller firms: (1) a fundamental change in the world economy, related to the intensification of global competition, the increase in the degree of uncertainty, and greater market fragmentation, and (2) changes in the characteristics of technological progress. As a consequence, new areas of interest emerged and topics like entrepreneurship, innovation, industrial dynamics, and job generation (Acs, 1992) came to dominate the political debate. This development received additional support from politicians such as Ronald Reagan in the United States and Margaret Thatcher in the United Kingdom, who pursued a policy strongly in favor of promoting small business and entrepreneurship. It was in this context that entrepreneurship research per se began to develop. David Birch, in his path-breaking report The Job Generation Process (1979), found that the majority of employment opportunities in the United States were created by small and young firms not large companies; Zoltan Acs, in The Changing Structure of the US Economy: Lessons from the US Steel Industry (1984), argued that small firms had an innovative role in the economy as agents of change; and Michael Piore and Charles Sabel May,

8 in The Second Industrial Divide (1984), a macrohistorical analysis of the transformation from Fordist mass production to flexible specialization using the Italian industrial districts, made the phenomenon of entrepreneurship and its connections with underlying changes in society visible and, in a research sense, manifestly attractive. As a consequence, a large number of enthusiastic researchers with different backgrounds and different interests began to research in this new area. The growth of the field, had begun. This early development of entrepreneurship as a research field could be described as Individualism, i.e., the research community was small and fragmented. Entrepreneurship research was, to a great extent, dependent on individual initiatives and projects. Importation of knowledge, i.e., entrepreneurship research had not developed an identity of its own. Instead, it was strongly influenced by the mainstream discipline s terms, concepts, models, and methods. Discovery-oriented research, i.e., a focus on providing descriptions and insights about a phenomenon that was previously unfamiliar. The level of methodological sophistication and theoretical analysis in most of the studies was quite low. In the next section, we describe and analyze the development of entrepreneurship research since the mid-1980s with respect to the research front and knowledge base. We have used three 5-year citing windows, the periods from 1986 to 1990, from 1993 to 1997, and from 2000 to The Period Figure 3 presents those researchers who were cited more than five times in the period between 1986 and Of the 59 researchers shown on the map in Figure 3, 14 or nearly 24% are outsiders, i.e., researchers cited by entrepreneurship researchers but not citing them, and the others could be regarded as insiders indicating entrepreneurship researchers citing other entrepreneurship researchers. As stated previously, the size of the circle indicates the number of citations received with larger circles showing authors more commonly cited. Circles that are closer to each other are more commonly co-cited. The Research Front The research front, during this period, can be determined by assessing the content of the five clusters resulting from a single-link-clustering routine (Bibexcel, a bibliometric software available at These clusters, and the authors associated with them, are subsequently described. Research clusters 1. Business startups and specifically in the problems of ethnic entrepreneurship (Aldrich, Light, Min, Portes, & Waldinger). 2. Entrepreneurship from an economics perspective, particularly entrepreneurship in economic theory (Baumol, Casson, Freeman, Kent, & Ronen). 3. The process view on entrepreneurship, new venture development, emerging organizations, new venture strategies, and the performance of new ventures (Carland, Chrisman, Dess, Gartner, Guilder, & Sandberg). 4. Employment and regional development in the U.K. context (Keeble, O Farrell, & Storey). This research specialization has remained throughout all three periods examined and follows the tradition of Birch. 382 ENTREPRENEURSHIP THEORY and PRACTICE

9 Figure Clusters of Entrepreneurship Researchers 5. The remaining 34 authors, clustered together, were loosely focused on determinants of entrepreneurship, whether in the small firm or in the corporation. While a rather eclectic grouping, they appear to have been brought together due to a common reliance on a similar knowledge base as discussed in the next section. Knowledge Base The largest cluster included the major cited researchers of the period. Two central research themes among this eclectic larger grouping could be identified; one group of researchers making the phenomenon of entrepreneurship visible without any basic knowledge base, more than their background in management studies in a broader sense, (e.g., Vesper, Cooper, Hisrich, Birley, & Sexton), and another group focused on corporate entrepreneurship (Burgelman, Kanter, Miller, Pinchot, Drucker, Stevenson, & MacMillan). May,

10 Table 1 Core Authors and Citation Levels Cited author Total Aldrich, H.E Light, I Portes, A Cooper, A.C Waldinger, R Gartner, W.B Kanter, R.N Porter, M.E Seventy-six percent of the researchers included in Figure 3 were insiders, citing and being cited by each other. Seven of these early insider researchers (and one outsider, Porter) made it into the top citation statistics overall (the upper 50% of citations made from 1986 to 2004). These are the researchers who could be considered a foundation or core group of researchers from the beginning of our period of analysis. If one looks at the overall citations they received throughout the entire period under examination, it can be seen that their influence only increased over time (Table 1 1 ). Not every highly cited individual (with more than 50 citations overall) was cited sufficiently often in each period to be included in following maps (Figures 4 and 5). For example, Light, Portes, and Waldinger appear to have provided the foundation for research into ethnic studies (cluster 1 in this period), yet Waldinger, despite his 69 total citations, drops off our maps in the final period where scholars had to be cited a minimum of 20 times between 2000 and Another small group that focused on the psychological traits of the entrepreneur (a field that metamorphosed into the mainstream of research in the period) retained only one founding researcher in the next period (Gartner). Authors such as Dess continued to be cited in the next two periods, but not often enough to be included on the new maps with their relatively random 2 citation cutoffs. Transients and Other Contributors There are numerous ad hoc transients or researchers who have, at some point, written in the entrepreneurial literature, but who have been cited minimally if at all. Influential transients would include researchers who, while largely cited within the field during a brief period, do not continue to contribute to it over time. This would include 17 of the 29 researchers shown in the map for who drop out of the citation window in the next period, researchers such as Venkatapathy and Pinchot. 1. The total column in Table 1 refers to the entire period from 1982 to 2004, i.e., it is inclusive of all periods in the citation windows, not just those citations occurring in the periods selected for analysis. 2. The cutoffs on each map were determined by a need to keep the number or names included legible, thus reducing the number given per map to between 55 and 60, depending upon the nearest available citation level (5 in , 11 in , and 20 in ). 384 ENTREPRENEURSHIP THEORY and PRACTICE

11 Figure Clusters of Entrepreneurship Researchers Twelve of our 29 drop-outs were influential outsiders or individuals that were cited by authors within the group but did not, themselves, cite entrepreneurial scholars, including Drucker and Sexton who, despite their influence in the first period, do not continue to be cited by entrepreneurial researchers to the same extent in later periods. Drucker, e.g., with one of the largest circles in this period due to 24 citations made to him between 1986 and 1990, had 43 references made to him over the entire period, and these were decreasing over time as his authority was superseded. Additional categories could be developed among entrepreneurship researchers themselves including those who publish in the entrepreneurial literature over the longer term and who are occasionally but not commonly cited, to a range of more commonly cited authors including the core entrepreneurial researchers who form the knowledge base previously mentioned. Between 1986 and 1990, 299 separate articles were written using our key term entrep*. Of these, 82 were never cited and another 94 were cited fewer than the five May,

12 Figure Clusters of Entrepreneurship Researchers times used in our cutoff for the period. Clearly, some of these articles picked up advocates in later periods as can be seen by the example of Bates, whose four early citations expanded, in later periods, to show that his research did, indeed, contribute to scholarly endeavors in ethnic entrepreneurship. Thus, those insider authors who continue to be cited over more than one of our periods, but who have not been cited more than 50 times, are considered contributors. The Period The proportion of outsiders to insiders has, in the period between 1993 and 1997, dropped about 10% (from 24 to 14%). Only eight of the 54 authors are cited by but not 386 ENTREPRENEURSHIP THEORY and PRACTICE

13 citing other entrepreneurship researchers. This decrease in outsiders shows an increasing reliance on a more developed research community, one that has strong researchers of its own now shaping the entrepreneurship research agenda. The map that is subsequently presented shows the number of clusters existing in the period (Figure 4). Again, there is a large and relatively eclectic central cluster as well as a number of researchers identified with more distinct specializations within entrepreneurship research. The Research Front The clusters in this new time window include 1. Studies examining ethnic entrepreneurship, made up of an expanded group that retained three of its original five proponents (Light, Portes, & Waldinger) and attracted four additional advocates (Kornai, Nee, Evans, & Bates) who actively cite and are cited within the field during this period, although they drop out of the window in the final period along with Waldinger. 2. The second cluster from 1986 to 1990 that focused on environmental factors affecting entrepreneurs developed into two additional ones in this period; the first is a much larger cluster (12 commonly cited individuals). Baumol was still in this cluster but was now more closely linked to the research being done by Bull or, at a further remove, by Hart and Aghion. We can also find a group of researchers focusing on the venture capital market such as Sapienza, Mason, MacMillan, and Bygrave. These authors are also linked with researchers with a stronger management focus like Kanter, Mintzberg, Larson, and the outsider Williamson. 3. The smaller cluster still focused on affective environmental factors and was intellectually related to the same cluster as the previously mentioned one, consisted of only five researchers (Harvey, Cox, Leitner, Cooke, & Amin) with an interest in regional development, the Italian industrial districts, local specializations, and regional innovation networks. This group also contained one commonly cited outsider (Cox). 4. Another small cluster developed during the period with a focus on innovation and regional development (Audretsch, Acs, & Florida). This issue is developed further by five different researchers in , while two of the three researchers from this period, Audretsch and Acs, move on to the even more specialized but related area of knowledge clusters (spin-offs, industrial parks, etc.). 5. A final small cluster, consisting of only three researchers, is made up of Covin, Stevenson, and Zahra. These researchers had a focus on corporate entrepreneurship and performance, much like the larger grouping of the final eclectic cluster from the previous period. Interestingly, none of these authors have stayed within this narrowly defined area of research. 6. Finally, a larger eclectic cluster of 22 insiders and outsiders have examined a number of other issues which seem related to the psychology of the entrepreneur and various institutional factors contributing to their development (networks, strategy, conditions for formation, and special needs of women or of corporate entrepreneurs). The group is centered around Cooper, Aldrich, and Gartner (the most cited authors in the cluster) and extends from Aldrich to Low and Hannan, to Reynolds and Storey, to Solomon and Johannisson, to Brush and Birley, and to Porter. From Gartner, this cluster extends to Timmons and Vandeven, Vesper, Amit, to McGrath and Shane, or McGrath and Hamel, and to Block, Venkataraman, and Kogut. May,

14 Table 2 Core Authors and Citation Levels Cited author Total Shane Aldrich Audretsch, D.B Light, I Zahra, S.A Portes, A Bates, T Cooper, A.C Waldinger, R Gartner, W.B Kanter, R.N Porter, M.E Acs, Z.J Reynolds, P.D Venkataraman, S Knowledge Base The development of the knowledge base is now more established. There are fewer outsiders, and we can assume that researchers have begun to build on the foundations established by previous researchers in their own discipline, contributors, and core entrepreneurial researchers, rather than drawing outsiders from the broader management and economics arena. More interesting than the topics of research, not always readily grouped into neat classifications, is the continuance of authors being cited over the periods examined and their, at times shifting, allegiances to particular subdiscipline areas within entrepreneurship (see Table 2). Fifteen individuals from our top half percent of highly cited researchers were being cited in the period between 1993 and Nearly half of these have carried over from the previous period. Four continued, as indicated previously, to form the knowledge base for those researching ethnic issues in entrepreneurship. Bates, as noted, was only just under the cutoff in that previous period. Seven of the 15 most highly cited individuals were cited in the largest cluster of the period (Shane, Aldrich, Cooper, Gartner, Porter, Reynolds, & Venkataraman). Of the remaining four oft cited researchers, two were cited by those concerned with self-employment and with the role of the small firm in economic development (Acs & Audretsch); one (Kanter) was cited in regard to policy studies about finance for innovation (an issue that developed further in ), and one (Zahra) was cited in measuring the effectiveness of entrepreneurial performance. Transients and Other Contributors More people were writing about entrepreneurial issues in this period with 1,082 articles written, a nearly fourfold increase in publications. The number of articles that could be classified as being written by ad hoc transients also increased, more than 388 ENTREPRENEURSHIP THEORY and PRACTICE

15 doubling in number (the proportion, however, remained about the same over both periods). Over 22% of the 1,082 articles failed to be cited at all, while another 36% were cited fewer than five times. Another 213 authors were cited between 5 and 10 times. These authors, who managed to provoke some interest in their scholarship by other entrepreneurial researchers, could be considered influential transients as they generally failed to be cited over more than one period. Of the 53 authors included on our map (Figure 4), only one (Bull) is cited solely in the period and is therefore considered an influential transient. By contrast, six authors (Bygrave, Larson, Covin, Amin, Birley, & Van de Ven) were cited over all three periods. An additional eight authors were cited over more than one period, but did not themselves cite other entrepreneurial authors and are thus influential outsiders. In all, 31 of the researchers shown on the map are contributors, defined earlier as insiders cited across at least two periods. Authors cited on this map wrote a total of 228 articles, far fewer than those written by ad hoc transients. However, the number of references made to them by other researchers reinforces our understanding of their importance in the development of entrepreneurship research. Fifteen of those included on the map are core authors (i.e., see Table 2), two of whom, Reynolds and Porter, are outsiders. The Period In this final period, the outsider ratio has been substantially reduced with only 7 of the 57 researchers (9%) identified as outsiders. Additionally, the number of specialized clusters has again increased, as subsequently shown in Figure 5. There is more continuity among researchers and research clusters from the period through the period than there was between the previous two periods. Many of the mapped authors from the period, those cited at least 11 times in that period, have also made the cutoff for the following period having been cited at least 20 times therein (placing them in the top 3% of cited authors). The Research Front The largest cluster of co-citations is smaller than in previous periods, and there are a greater number of smaller clusters. This indicates, to us, that the field is becoming more specialized and, given some of the new entrants, may also be attracting those from a broader array of disciplines than was previously the case. The research front, thus, has split into more narrow specializations and, within these, we find new entrants, including outsiders, such as Gompers, being attracted to entrepreneurial research due to its intersection with their previous focus (in this case, finance). Whether these people, now commonly cited, will become part of the knowledge base for future entrepreneurship researchers, only time will tell. However, from the number of citations they are currently receiving, their contribution to the research front is important. The seven separate smaller clusters in the period include 1. Innovation and regional development (Acs, Audretsch, Cooke, Feldman, Malecki, Porter, & Reynolds), a specialization that appears to have come from a merger of clusters 3 and 4 in period The research focus on this area appears to be growing. May,

16 2. Sociology and the place of capitalistic endeavor (Brenner, Castells, Jessop, MacLeod, & Peck). Most of those in this cluster were first cited in the latter part of the period but were not commonly cited until the period. The focus of those citing them, researchers whose interest is on the development of economies and on the role of capitalism, appears more sociological. 3. Strategic entrepreneurship, management of resources, and venture performance (Autio, Deeds, Hitt, Johannisson, Lumpkin, Peng, Teece, Westhead, Wright, & Zahra). Many of those cited in relation to corporate entrepreneurship (the fifth cluster from 1993 to 1997) are now included in this cluster. It appears to have been a further refinement of the concepts that were developed in that period, examining performance and the utilization of resources, including social capital. Not only are there larger numbers of researchers involved in this field, but there is also more syndication of research with coauthorship extending across clusters. 4. A continuance of interest in ethnic entrepreneurship, still led by Light and Portes, but also including Ram and Rath. This cluster appears to be shrinking with ethnic entrepreneurship retreating from the research front. 5. Legal aspects of entrepreneurship, policy implications ( Johnson, Khanna, & Laporta). This is a new area of interest with researchers focused on the legal aspects of entrepreneurship. This area, while including Johnson as an insider, is dominated by two outsiders, Khanna and Laporta. 6. Self-employment and regional development are continued in this final period (Blanchflower, Demeza, Fairlie, Hamilton, & Taylor). None of these authors were commonly cited until the final period of our analysis, but despite this, all are in the top 3% of cited authors, and Blanchflower is in the top 50%. 7. A financial cluster (Gompers, Hellmann, Kaplan, Lerner, & Mason) ends the small clusters in this period. This seventh cluster comprised researchers who have concentrated on venture capital, angels, and financing for high-technology small firms. It is a direct descendant of the financing entrepreneurship cluster but, as appears to be usual in the development of these research areas, has been more narrowly focused. The outsider, Gompers, is a leading researcher in the area of venture capital financing (Cornelius & Persson, 2006) but has been more focused on investors rather than on entrepreneurs. 8. The large eclectic cluster in this period consisted of 18 researchers who are, with one exception, insiders citing and being cited by each other. Two of those in the cluster, Aldrich and Venkataraman, have been in the mainstream of entrepreneurial research through two windows (Aldrich having also participated in the smaller ethnic cluster in the first period examined). Knowledge Base Of the 14 highly cited authors who continued to be or became of interest to researchers in the period, 10 were also highly cited in the period, and four were highly cited in our earliest period ( ) (see Table 3). Thus, we can see the emergence of core researchers within the field. Four of these researchers were cited in regard to economic development or the development of business (knowledge) clusters. Audretsch and Acs had been cited in business development research in the previous period and were joined, here, by Reynolds (who had previously been cited in mainstream entrepreneurial research) and the nonentrepreneurial researcher, Porter. Blanchflower, a new face in the citation reports, was taken up by those interested in self-employment, another spin-off of the business development research of the previous period. Zahra, who 390 ENTREPRENEURSHIP THEORY and PRACTICE

17 Table 3 Core Authors and Citation Levels Cited author Total Shane, S Aldrich, H.E Audretsch, D.B Light, I Zahra, S.A Portes, A Blanchflower, D.G Gompers, P Hitt, M.A Porter, M.E Acs, Z.J Reynolds, P.D Hellmann, T Venkataraman, S had been cited in regard to effective entrepreneurial performance, was now embraced, along with another new entrant, Hitt, by those examining corporate entrepreneurship and networks. Three researchers focusing their interest in synthesizing and theorizing entrepreneurship research, Venkataraman, Shane, and Aldrich continue to be cited by mainstream entrepreneurial researchers in the period just as they had been in the one. Two other new faces, Gompers and Hellmann, drawn from the finance milieu, entered the annals of entrepreneurial research as interest in venture capital, angels, and the financing of high-technology small businesses began to draw the interest of entrepreneurship researchers. While ethnic studies continue into , the citation references to our leading researchers, who comprised this knowledge base, began to drop off quite severely. Transients and Other Contributors The number of entrepreneurship articles written in this period continued to rise albeit not as quickly, with 1,785 new articles written on entrepreneurship. Over 88% of these articles were, by our definition, written by ad hoc transients; nearly 53% of the authors were never cited. Less time has passed since publication of these articles, of course, which may account for the higher proportion of transients. Again, given the time frame, it is difficult to assess how influential any of these authors may be or the number of years in which their work will continue to be cited. A number of new authors (153) were first cited between 11 and 19 times during the period. This would have resulted in their inclusion on our map (Figure 5), had they been cited in that period. They would appear, therefore, to be researchers of some influence, although they cannot yet be identified as contributors, given the single period in which their citations have occurred. May,

18 Referring to citations alone, the 56 scholars included on Figure 5 were cited a total of 1,145 times, not all citations referring to articles published during this period. Our 14 core authors accounted for 21% of the total citations between 2000 and Two of these, Porter and Gompers, were cited by, but not citing other, entrepreneurial authors. Of the entire group included on the map, the majority are contributors, having been cited over at least two periods (77%), while one quarter have been cited across all three. Of the 13 who have just begun to be cited in the period, one (Hellmann) is already considered a core author. Three others, Dyer, Khanna, and La Porta, are outsiders, their influence over time yet to be determined. Only Castells, cited over two periods, can currently be labeled an influential outsider. The percentage of citations made to outsiders in this period decreased by only 2%. Analysis Development of the Research Community The increase in the number of researchers interested in the field of entrepreneurship in the 1990s was significant. The number of publications using the key term entrep* grew from 299 in the late 1980s to over 1,000 in the mid-1990s and over 1,700 in the early part of the current decade. Given the five-fold increase since that time, this growth has clearly not stopped. However, the growth since the mid-1990s has slowed with only half again as many researchers involved in the latest period. Many of these researchers can be regarded as transients, i.e., researchers who temporarily publish (never cited or minimally cited) in the area of entrepreneurship. Over 1,000 of the 3,941 articles included in this database have never been cited while 1,109 have been cited fewer than five times. Our analysis, however, went beyond these articles examining who was cited, by whom, and how often. While assessing the contributions of various entrepreneurship researchers, we divided them into four categories. We called researchers who write in the area of entrepreneurship but are either never cited or cited only minimally in a single period of time, ad hoc transients. Some researchers enter the field and seem to hold some sway, given a flurry of interest in their research in a single period, but do not continue to be cited over time. Among these researchers, those who cited and were cited by other entrepreneurship researchers were labeled influential transients, while those who were cited but did not cite entrepreneurship researchers, particularly if cited over more than one period, were called influential outsiders. The researchers who have been cited more than 10 times are proportionately few in number, making up only 6.5% of the total. However, even among these researchers, we have those who may inappropriately be considered transient due to having been cited in a very narrow window of time, e.g., Pinchot. Most of these researchers, however, have been cited often and have continued to be cited over a long period. Their contribution to research in entrepreneurship should not be discounted. We have called these individuals contributors. Our focus, however, has been on determining the names of the core researchers in entrepreneurship. We have chosen to include those who have been cited by entrepreneurship researchers more than 50 times, placing them in the upper 50% of authors cited. We believe that these people are the ones who ask the important questions and influence others to undertake research in the area. The names of our 19 core authors are given in Table ENTREPRENEURSHIP THEORY and PRACTICE