Given the exponential growth of publications “...research on college students is perhaps the single largest area of inquiry in the field of higher education...” (Pascarella, 2006, p. 508). Although college outcome literature expanded exponentially and there have been excellent extensive evaluations of the research on college students since 1973 (Pascarella & Terenzini, 1991, 2005; Mayhew et al., 2016) in a three-volume book. These comprehensive books indicate the sheer size and scope of the research trends in college outcomes for over half a century. Pascarella noted that the “huge and complex body of research on college students is expanding at an accelerated rate” and it is “encyclopedic” (2006, p.508) while he predicted that there would be up to 10,000 studies produced in two decades.

Pascarella (2006) also pointed out that although their syntheses worked quite well in the past, because of the high rate growth in the number of publications. However, it would be impossible to carry out such syntheses by one or two individuals. Even conducting reviews takes 1-2 years and a considerable literature emerges during the review periods. Pascarella suggested either professional organizations may undertake such reviews with 10-20 scholars or reviews of smaller scale may be conducted:

...to break the huge body of research on college impact into more manageable segments and conduct literature reviews in a continuous and overlapping manner rather than in the periodic, serial pattern that has characterized past efforts (Pascarella, 2006, 517).

 A number of systematic reviews carried out in higher education recently (Tigth, 2020). However, the majority of them focused on student health. Other studies focused on a specific group of students such as at-risk (Valentine et al., 2011), stress management (Amanvermezet al., 2020), mental health (Worsley et al., 2020). These reviews add our knowledge around specific issues such as intersectionality (Nichols & Stahl, 2019), diversity (Duran, 2019); Special needs (Nuske et al., 2019), critical thinking (Calma & Davies, 2020), reform (Heinz & Maasen, 2020), employment (Vick & Robertson, 2018), student engagement (Aparicio et al., 2020), and social networks and social capital (Mishra, 2020) on college students.  These reviews also tend to focus on the findings of one country studies, i. e., the US or developing countries (Unterhalter & Howell, 2020).

Despite the sheer size of the literature on college students, there were few studies focused on the structure and processes from the sociology of science perspective. Although the current study cannot have the breadth and the depth of the books that synthesize the research produced in decades (Bowen, 1977; Feldman & Newcomb, 1969; Pascarella & Terenzini, 1991 & 2005; Mayhew & Colleagues, 2016), the current study provides an overview of the literature.

The purpose of this study is to systematically review the research on college student outcomes and to explore the distribution of the studies methodologically and to identify conceptual trends of student outcomes in higher education context. As a result, the research questions may be listed as below:

Research Question 1: What is the volume, growth trajectory, and geographic

distribution of higher education journal literature based on student outcomes between 1960 (technical genesis of database) and 2020 when higher education literature received a corpus of studies and was referenced by many scholars in science mapping literature?

Research Question 2: What journals, authors, and articles on student outcomes have evidenced the greatest citation impact over the past six decades?

Research Question 3: What is the intellectual structure of the higher education knowledge base on student outcomes?

Research Question 4: What topical foci have pertinent to student outcomes attracted the greatest attention from higher education scholars between 1960 and 2020?

Content analysis was used as the research design in the current study to achieve the purpose of the study. According to Cohen et al.(2007), content analysis is a technique to summarize data coming from many studies. Bibliometric analysis is a way to support empirical investigations of the process and structure of fields or knowledge base. Bibliometric methods provide diversity in conceptualizations and modeling to explore foundations, intellectual core, and directions for future research of a typical research field such that these methods offer complementary accompaniment to traditional literature reviews which are non-adequate to present holistic perspectives and to generate new knowledge (Aparicio, Iturralde, & Maseda, 2020; Serenko &Bontis, 2013).The current study combined them as bibliometric content analysis to document trends in concepts and methodological approaches of research in higher education field in terms of college student experiences. The review was delimited to articles published in higher education journals. Books, book chapters, proceedings, conference papers, dissertations, and reports were excluded. Since journal articles are kept in the databases comprehensively and broadly. Further, journals were delimited to the Scopus index. The reason why Scopus was selected was an opportunity to generate databases for systematic reviews as Mongenon and Paul-Hus (2016) emphasized. Considering Scopus-indexed higher education journals, 52 higher education specialization journals were identified. However, search criteria excluded the journals out of education. As a result, 52 journals were included in the review. In order to identify sources, PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-analyses) developed by Moher, Liberati, Tetzlaff, Altman, and PRISMA Group (2009) was followed. This way to review studies has four steps: identification, screening, eligibility, and inclusion for synthesis. For the identification step, the following parameters were conducted: inclusion of time period (1960 to 2020), inclusion of selected journals, inclusion of articles as document types, and exclusion of commentaries, books, chapters, proceedings, conference papers, dissertations, reports, and editorials. For the screening step, the keywords which are “college students”, “higher education”, and “student outcomes” were searched. In this step, 2396 studies were screened. An eligibility check was performed in the third step such that 21 documents were excluded. Finally, 2375 articles were included for bibliometric synthesis.

Intellectual structure of higher education knowledge base in terms of student outcomes was examined within “author co-citation analysis”. For this purpose, VOSviewer was performed in order to generate co-citation map visualizing similarities of research by HE scholars. A threshold of at least 50 citations with a display of 167 authors was selected. As Figure 3 depicted, the maps classified authors into clusters such that there were five clusters which were named by the researchers of the current study. Density of links connecting scholars was proportional to the number of times a scholar was co-cited with another scholar. Further, density of links connecting clusters referred to interconnectedness of HE knowledge base on student outcome. In naming clusters, both coding and categorization procedures in content analysis and common perspectives in the literature were followed. By considering positions of clusters which were provided by VOSviewer in terms of interconnectedness of knowledge base, names of clusters were placed in the author co-citation network map. The first cluster included 44 articles and was called as the quality of student learning. The second cluster consisted of 43 articles and was called as student retention. The third cluster had 33 articles and was named as student demographics. The fourth cluster had 26 articles and was called as inequality of opportunity. The final cluster included 21 articles and was named as diversity. Co-word analysis was adjusted to concepts in titles, keywords described by authors, and index keywords. In the analysis, a threshold of at least 10 co-occurring cases of a keyword such that the 63 most frequently co-occurring keywords were displayed. The most commonly five co-occurring keywords were higher education (n = 389), retention (n = 54), assessment (n = 53), diversity (n = 51), and college students (n = 50). Higher education was also the keyword having the highest total link strength.

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