1. Introduction
A formal definition of brain drain is one that offers the thesaurus of the Education Resources Information Center-ERIC [
1] as the “Loss of highly skilled or educated persons from one country, region, institution, or job sector to another, based on better pay, improved living conditions, expanded opportunities, between others”. Many influences generated locally and globally govern brain loss at the international level [
2]. The loss of educated people can be associated with a lack of institutional capacity to absorb and use advanced intellectual capital [
3]. The phenomenon generates a decrease in the intellectual capital of the country of origin, but at the same time, an increase in political instability and the degree of fractionation of that country [
4]. Its measurement focuses on the migration of nationals with tertiary education, but mainly in physicians and professors [
5].
In the mainstream literature, it is possible to identify as initial studies on the phenomenon known as ‘brain drain’ carried out by Johnson [
6] publishing in Minerva. Johnson reports the severe implications, beyond the loss of public investment and effects on the salaries of state officials, expressed in the British concept of the ‘brain drain’ phenomenon of emigration of health personnel and universities generates on Canada’s social welfare. In turn, the author remarks that the concept of ‘brain drain’ is not exempt from the nationalist roots observed in the discussion of the phenomenon. Furthermore, Oteiza [
7], publishing in the International Labor Review, raises the costs for a less developed country, as in Argentina’s case, in the emigration of engineers. Oteiza [
7] shows that this brain drain has negative implications on the country’s developmental possibilities.
On the other hand, Grubel [
8] reflects on the USA’s role as a destination country for the brain drain and the effects of said immigration on the international scene. Finally, Perkins [
9] comments in Foreign Affairs magazine, based on International Relations, with perspective. In this, Perkins associates the Brain Drain phenomenon with the developmental possibilities of a nation and the limits to development in regions with low levels of advanced intellectual capital. The author argues that these countries are affected by the brain drain because people seek better personal development conditions.
Except for the cited work by Johnson [
6], there are just a few works that could connote greater interest in the international scientific community. In Johnson’s publication in Minerva, the document’s citations in high impact journals (JCR-WoS) amount to around 50 citations to date. In the mid-1970s, the Portes [
10] document arouses similar interest in citations to date. The authors’ interest relates to the novelty that implies identifying specific determinants of a social phenomenon, such as brain drain. In any case, the article that elicits the most significant connotation in the first three decades of brain drain studies to date is the proposed economic model of Kwok and Leland [
11]. Kwok and Leland’s work mentioned above is still used today as part of some countries’ public policies [
12]. Among the policy implications, the authors mention: (1) A government information policy on foreign educational programs, which helps employers in the “qualification” of each graduate abroad’s records. (2) Scholarships abroad with a “return clause”, although it may be difficult to enforce them, and a “forced“ return may entail other costs to society and may even distort scholarship applications leading the best students to seek other sources of help. (3) Return subsidies offer various benefits to students who do return, thus contributing to private placement with lower initial costs for the employer. However, in ignorance of the real effect on the individual decision to return to the country of origin, it can involve a costly universal application. Furthermore, (4) Development of elite educational programs that balance the gradient of educational quality prompts emigration, and it is a form of recognition of extraordinarily talented students’ abilities since that high talent tends not to return [
11].
Interestingly, in recent years, the topic of brain drain has gained such momentum that it has become necessary to adopt tools and methods to characterize a phenomenon that has been defined as dynamic and changing [
13]. This resurgence of academic production motivates us to take a new look at this dynamic and changing phenomenon. Therefore, in the present work, we systematically study Brain Drain, e.d., theoretical approaches about the Advanced Intellectual Capital international migratory phenomenon.
In particular, the physicians’ emigration, this phenomenon affects human development indicators in developing countries, ed. infant mortality and vaccination rates. Mortality and vaccination rates are causally related to physicians’ more significant number [
14]. As Sherr et al. [
15] point out, qualified intellectual capital is essential for the proper functioning of health systems, and its absence undermines the public health sector. It is a fact that this phenomenon mainly affects developing countries from where do migrants flow to rich countries. The cited flow and imbalance are not merely a qualified human resources global management problem. Flow and imbalance phenomena are related to uneven global development. Uneven global development leads to unequal global access to quality healthcare deepening unsustainability in some geographies [
16]. Because it affects economic sustainability for life and sustainability for social equity [
17], generating fragility to the sustainability of those states [
18].
In the case of professors, it is crucial to study why do scientists choose to look for another “better place” to carry out their research [
13]. Along with this, authors recognize that the strengthening of specific academic disciplines demands incorporating professors trained abroad. This strengthening is sought by higher education and research institutions due to the influence of having an international faculty [
19]. Therefore, it is of high interest to know the proportion of immigrant teachers in the entire teaching staff, the variations by discipline, the differences in foreign teachers’ research performance in the academic system, and possible top-level foreign scientists’ concentrations. Likewise, it is also relevant to study the proportion of foreign teachers who are unproductive or with a mediocre performance. The study of professors and scientists’ loss will provide information to analyze national policies related to the higher education system’s attractiveness and understand the phenomenon of entry and flight of qualified foreign professors, especially in countries with continuous brain drain on their borders [
20].
The mix of factors to leave one country and choose another as a destination is complex [
21]. Among the multiplicity of factors are comparative monetary benefits, the quality of family and individual life, the perception of better prospects for future generations, and social freedom and a liberal atmosphere. These parameters are recognized as crucial to affect decision-making [
2,
11,
22,
23]. Besides, in the academic sector, working in an excellent organizational climate, i.e., the search for job satisfaction inhibits the propensity to migrate, favoring job satisfaction with an administration that favors simplified procedures, research productivity, harmonious academic standards, and a meritocratic reward process [
24].
As for the already mentioned factors that explain the brain drain, one can add the professional and academic ties with peers that remain in the country of origin and their propensity to return, in a reverse migration. Altogether, those factors give way to a brain drain and a more complex and dynamic phenomenon called brain circulation [
21]. Saxenian [
25] already recognized that the connections with the countries of origin, the circulation of brains, and the possibilities of telecommunication lead to a knowledge transfer toward destinations at peripheral areas of knowledge generation achieving cross-border cooperation. Saxenian [
25] exemplifies such phenomenon with Chinese and Indian engineers that contribute to their countries technological development working from Silicon Valley. These circular actions of highly skilled migrants -HSM- in favor of developing their country of origin show a correct level of commitment that does not seem to diminish with time [
26]. In fact, in some cases, this circulation is definitively imposed in the form of brain gain, which depends on the availability of some resources to finance certain research activities, on the offer of doctoral programs with international mobility or other international mobility programs [
7,
27].
Delivering a more critical point about the phenomenon of brain drain and brain gain has been analyzed and studied, Metcalfe [
28] has pointed out that the disconnection between body and mind implied in the literature marginalizes the political identities of researchers as foreign citizens and their energies, affections, desires, and imaginations. Studying the brain drain phenomenon entails an understanding of academic mobility because of national strategies of innovation and economic competitiveness, affecting the sustainability in its technological development subdimension [
17], and which leaves unexplored the epistemic and ontological change at the individual level. Instead, a nomadic political ontology approach permits academics’ mobility to analyze the interrelations between nationalism, academic belonging, and transnationalism.
Many countries consider the brain drain phenomenon a fundamental problem of their economic policy [
29]. This consideration about economic policy strengthens discussions regarding the possibility of reversing the brain drain and its impact on the economy [
5,
30]. Such an approach is becoming an increasingly crucial governmental concern to sustain vibrant economies and societies [
31]. Furthermore, in some countries, the government decides to face a brain drain, given tertiary students’ emigration [
32]. Emigration of tertiary students has come to undermine national capacities to provide essential services in poor states, even implying a justified restriction to limit the flight of the minority of cases that this type of migration implies [
33]. Problems with emigration are more substantial in small countries that are geographically close to the central regions of the Organization for Economic Cooperation and Development (OECD) that share colonial ties with OECD countries, and that direct most of their migratory flows to countries with selective quality immigration programs [
4]. Nevertheless, the OECD countries do not always, or not all, obtain only brain gains, since some are affected by flows between them; for example, the flow of European academics to US universities [
30].
On the one hand, some governments consider the brain drain phenomenon as an economically productive phenomenon, based on remittances and direct transactions received by highly qualified human resources based abroad [
2]. Moreover, on the other, the countries wish to create the conditions to promote and strengthen the productivity gains necessary to sustain economic growth, and they must be aware of how much and how quickly an uncontrolled academic implosion can occur [
30]. In the same sense, brain drain or rather brain circulation, depending on their scientific experience abroad, can contribute to shaping local scientific systems, recognizing the potential of highly skilled migration to improve the development of a national academic system or at least the strengthening of specific disciplines [
13,
19]. In this sense, Stark et al.’s [
34] findings show latency as regards the migratory freedom of highly qualified workers; brain drain and brain gain coexist; it can result in a higher average level of intellectual capital per worker in the country of origin. The higher intellectual capital per worker results from the asymmetry of information, the breadth of opportunities, and the structure of incentives. Also, the knowledge acquired by migrants abroad can return to their country of origin through diaspora networks [
35], and the application of intellectual property rights increases the chances that brain drain becomes into brain gain [
36]. Although in the face of academic mobility decisions, the scientometric impact of the science, technology, and innovation (ST&I) infrastructure has priority over the quality of life in the host country (Human Development Index, HDI). The combination of influencing factors gives complexity to government policies concerning national investments to address the flight and brain gain since both aspects must be considered [
37].
The consolidation of national science and technology systems and their scientometric results are related to the formation of intellectual capital and brain circulation management [
38]. Furthermore, bibliometric methods allow the study of brain drain at the micro-level and even adopt a scientometric approach that contributes, through the study of elite mobility, to understand its effects and implications in scientific policies [
39,
40]. Current studies of brain drain using scientometrics and bibliometrics methodology, in mainstream journals, focused mainly on the field of Information Science and Library Science [
39,
41,
42,
43]. Thus, assuming a proper approach to bibliometric or scientometric studies, these studies focused on the geographical mobility of scientists based on their affiliations [
27,
39,
42,
43], the effects on citation impact, academic collaboration, and competence [
41,
44,
45], and its effects on national scientific and technological sustainability [
46,
47].
To be precise, this article’s contribution to previous scientometrics studies is to address the brain drain phenomenon with a panoramic view. Furthermore, the present study approaches the brain drain phenomenon understanding it as a field of study by itself. Such a panoramic view is possible using massive metadata obtained in a varied disciplinary range of publications and considering brain drain in the last 55 years. Therefore, the present study does not address the migration phenomena itself but understands how researchers studied brain drain conceptualization in their diverse disciplines.
The existing literature on the brain drain from the South to the North has found several mechanisms affecting developing economies. However, some of the newly discovered effects remain debatable due to limited evidence. Therefore, some authors suggest a need to examine further how brain drain influences the formation of intellectual capital and, together with it, study the secondary effects of this phenomenon on technology [
48]. Given the current possibilities of access to information and the abundance of metadata, there are new possibilities in science and technology studies and its measurement [
49]. Such an approach means using massive data to measure, with the facilitation provided by scientometric tools, the concept of Brain Drain in the publications of the last 55 years. A scientometric study based on the abundance of metadata available today will allow us to ask the following research questions:
- RQ1.
Is there a critical mass of scientific research regarding the brain drain phenomenon?
- RQ2.
How has the study of the brain drain phenomenon evolved thematically and conceptually?
- RQ3.
Is it possible to identify classic authors on this topic? Are we facing the emergence of new reference authors?
2. Methodology
This research uses Scientometry as a systemic approach to understand trends in brain drain knowledge production. According to Vega and Salinas [
50], this methodology’s main objective is to assess scientific evolution and development and judge scientific policies related to certain aspects of economics and society. From this point of view, the scientometric meta-analysis presented here focuses on brain drain studies. The research process takes Web of Science—WoS [
51] articles as a reference, given its recognized quality among researchers worldwide [
52]. The authors selected the SSCI-WoS dat base because regarding Scopus, the journals indexed to SSCI-WoS have a high indexation duplicity in Scopus. However, the Scopus journals, which do not present a double indexing with the SSCI base, these have not been considered because “Scopus covers a superior number of journals but with lower impact and limited to recent articles” [
53], (p. 24). In consequence, the analytic procedure of the present study preferred impact over number of journals.
Furthermore, this study methodology uses as the search vector [
54] the “brain drain” construct that is present in articles indexed at the Journal Citation Report (JCR) of Social Science Citation Index, SSCI -that includes 50 social science disciplines (WoS Categories).
Data were explored for a recovery period between January 1956 and 14 December 2020 (oldest recovery: 1965), considering a thematic search, Field Label TS. Following the recommendations of Archuby et al. [
55], the following search vector was used: (TS = (Brain NEAR/0 Drain)) AND Types of documents: (Article), Indexes = SSCI period = 1956–2020. Researchers obtained these records from 68 metadata fields extraction grouped as author identification, localization, affiliation; article/source identification, access, recuperation codes, citation; keywords, abstract, cited references, and funding (see
Appendix A). Later, researchers analyzed the data set, using bibliometric rigor, looking to see if the knowledge production increases or not and achieve a critical research mass in an exponential growth form (Density-independent growth) [
49,
50,
51,
52]. Later, researchers determined contemporary literature when articles were produced [
56,
57,
58,
59,
60].
Table 1 identifies each of these analytical methods [
61].
Research establishes the principles Web of Science Categories and its temporal trends, the prolific authors’ concentrations according to Lotka’s Law [
59,
62,
63]. Then, researchers establish nucleus journals according to Bradford’s Law [
59,
64,
65,
66,
67,
68,
69,
70]. Furthermore, researchers set thematic segments of journal concentration. Afterward, through the VOSviewer [
71,
72,
73,
74,
75]. In parallel, the process produces a thematic study, high-use keywords plus
® (KWP), keywords corrected by WoS- according to Zipf’s Law [
76,
77,
78]. Finally, the procedure produces a visualization with word cloud and relational graph de contemporary KWP [
79,
80].
In the final phase of this study, researchers use scientometry of quantity (production), quality (impact), and relationship [
50,
81]. Furthermore, researchers analyzed co-authorship at the level of affiliation with institutions and authors. Researchers also identify highly cited articles in this step according to the Hirsch index [
82,
83,
84,
85,
86,
87]. The Hirsch index allows researchers to determine the classics and relevant contemporary articles. Finally, using the VOSviewer tool, researchers analyzed text data composed of titles and abstracts to identify high frequency terms and their time evolution trends [
88,
89,
90].
4. Discussion
The article contributes to the study about the conceptualization of elites’ migratory phenomenon defined as brain drain, in a broader disciplinary scope that are 99 WoS categories with a focus and more detail on 24 of them. Instead, the article does not just focus on a single category of knowledge production. The specialties delimitations are recognized as a relevant problem in the study of the mobility of elites at the micro-level [
39]; thus, this article manages to differentiate itself from other contemporary studies that give coverage of specific disciplines, either in economics [
118], in artificial intelligence [
119], or communication [
120]. The present article contributes to the literature presenting a general and updated analysis of the brain drain concept usage and its expansion in the last 55 years. The study is reliable because using the database -see
supplements- any researcher can replicate the study. Researchers need to use the software and the agreed-upon measures to obtain a robust replication. Furthermore, considering the defined search vector, the results can even be updated for future studies. Consequently, it is reliable and contributes to the literature analyzing the massive metadata of previous research about brain drain. However, considering the brain drain concept in a panoramic and non-specific way. Such panoramic perspective understands brain drain as a social phenomenon mainly related to sustainable technological development, a sustainability type that has recently been studied within the SDGs framework [
121,
122,
123,
124,
125,
126,
127,
128,
129,
130].
In the same sense, from the study of data spatiality, contributions from authors from 102 countries are covered, which are reduced to 50 when applying the h-index and narrowing it down to the elite of researchers. This approach gives ground coverage by adding countries on the periphery of world knowledge generation [
47]. Such coverage allows departing from contemporary studies that cover the phenomenon of brain drain with a focus on a classic and limited nucleus of countries, mainly: Australia, Canada, China, New Zealand, the United States, and the United Kingdom [
42,
44,
46]. Finally, this study contributes to providing temporary coverage of 55 years (1965–2020). The various international scientific collaborations, resulting from the intellectual human capital mobility [
12,
131,
132,
133], constitutes a partnership that allows progress in global sustainability (17th SDG) [
134,
135,
136,
137,
138].
Regarding the thematic segments defined—Economics and Politics, Territory and Environment, Science and Education Studies and Health—some of these are consistent even with the first identified articles in this study Oteiza [
7] and Perkins [
9] from Economics and Politics journal, and Johnson [
6] and Grubel [
8] from Science and Education Studies journal. In the case of Health, the focus of the phenomenon from its inception on physicians makes the development of this specialized theme natural, even more so in the current global health situation. About Territory and Environment, and in terms of migration, coverage of the brain drain in demography and geography, though later, it is thematically natural [
92,
139]. Among all these themes, Economics and Politics, as in other social phenomena, is preponderant due to thematic economization, consistent with the recognition of the economy as the main engine of mobility of advanced human capital [
140]. Such WoS category alone represents participation in practically a third of the registered articles. Such thematic is how the two most prominent authors account for the economization of studies since they have an academic trajectory in this field in European Universities that are part of UNA-Europe, added an academic in Health in a North American -USA- University. She obtained her Ph.D. in the USA, while the other male authors obtained their Ph.D. in France. Both countries are among those with the highest concentration in the knowledge production indexed articles in brain drain studies. In short, a lag in Brain Drain studies and its effects on the sustainability of the economy and technological development, which has been widely surpassed by studies focused on Environmental SDGs (Resources and Enivronment) and economics for life, promptly GoodHealth and Well-being (3rd SDG) [
141,
142].
Results show that a set of studies focused on destination countries [
143,
144,
145] raises the necessity of a change of approach since these types of studies were initially raised based on the loss of advanced intellectual capital in the countries of origin. However, studies are currently rethinking their orientation to brain gain [
12,
145,
146,
147,
148,
149], and to ideas of migratory dynamics presented in the brain circulation [
12,
47,
146,
147,
150,
151,
152,
153,
154]. Results emphasize that policies and efforts need to change if policymakers look at researchers’ brain drain concept use. Researchers moved away from brain leakage and retention and now emphasize brain drain attraction and gain. Even more, researchers recently focused on the study of circulation by individuals’ decisions, even at the cost of objective well-being; that is now known as brain circulation.
5. Conclusions
The main objective of the present article is to systematically study the current theoretical approaches to the Brain Drain phenomenon. The study offers an answer to questions regarding critical mass existence of scientific research on the brain drain phenomenon, how has the brain drain study evolved thematically and conceptually, and if it is possible to identify classic and new reference authors on this topic. We operationalize the study through the next research questions:
RQ1. Is there a critical mass of scientific research regarding the brain drain phenomenon?
RQ2. How has the study of the brain drain phenomenon evolved thematically and conceptually?
RQ3. Is it possible to identify classic authors on this topic? Are we facing the emergence of new reference authors?
Results show that there were 1212 articles produced by 2400 authors that present an exponential growth knowledge generation process. That process adjusts by approximately 70%, achieving a critical research mass in an exponential density-independent growth form, with a nucleus of 33 journals that discuss deeply brain drain studies, conforming to Bradford’s law with a margin of error equal 1.1% that is considered not significant. Therefore, this study gives an account of the ‘territory’ where the global epistemic community is built on brain drain studies, from its various approaches, delimiting their products (articles), actors (authors) and spaces (journals). Furthermore, the study recognizes 65 articles with a high citation -according to the Hirsch index, h–index- by the full 156 authors’ knowledge production. These 65 high citation articles belong to a researcher’s group that would be the contemporary research front of this knowledge global community. Among these community, there are three distinguished authors through the whole dataset. Additionally, there are 59 historical articles (classic pieces) from those 65 highly citated articles. These classic pieces are located by age temporarily under the median or semi-period of obsolescence. Finally, the remained six papers could give way to potential new relevant references in the brain drain phenomenon.
From a thematic point of view, the research distinguishes four study segments that manage to delimit the focus of the discussion.
Table 4 shows those themes based on the 33 journals of the Bradford nucleus and their contributions in percentage. There are two original themes. The first is Science and Education Studies, and the second is Economics and Politics. The latter of these themes has a great preponderance in the volume of discussion. Another segment, Health, is heavily studied. This sector has a significant impact on brain drain. Another paradoxical theme that presents a later start is Territory and Environment, which among others, comprises the WoS categories of Demography and Geography. Additionally, to these segments, scholars widely use five terms in recent literature. The theme that raises the highest interest in brain drain discussion is “destination country” and its local effects on research and the strengthening of innovation and industry, in terms of the 9th SDG. The brain drain studies and their effects on the sustainability dimensions, present a global imbalance that is evident and must be overcome, especially in the social sustainability dimension terms, which is mainly absent, despite various social pressure movements in the last decade, which demand greater equity (SDGs: 4 Education, 5 Gender and 10 Inequality) and social development (SDGs: 11 Cities and communities, 16 Peace, Justice and Strong institutions, and 17 Global partnerships), in different latitudes of the globe.
Finally, and as a precautionary note, scholars need to be aware that beyond the change of direction in the national effects, they need to extend their analysis to other countries when countries consider themselves destination countries. For example, scholars must focus their analysis beyond countries with a high level of development, which constitutes a new challenge in this line of research toward the study of the effects of the brain drain in the peripheral areas of knowledge production, contributing to a better understanding of the phenomenon in those geographic areas and design new public policies, in the economic dimension of sustainability [
17], to strengthen innovation and local industry [
32,
47,
140,
155,
156,
157]. Likewise, public policies should be approached from a logic of adaptation to the global mobility of advanced intellectual human capital (brain circulation) and not only from a drain perspective [
12,
158] and with a greater emphasis on the intellectual human capital attraction policies and not principally focused on brains retention or forced return [
45], avoiding the research groups break [
159] and promoting geographically distributed research [
160,
161,
162,
163].
As a limitation, despite the large number of JCR-WoS articles analyzed (1212), privileging the quality in the journal’s selection [
52] generates coverage limitations and an opportunity to access information to studies in the working phase, please see the discussion in the methodology section. Thus, in future research, the authors plan to increase the opportunity for early access to information by also incorporating proceeding documents (conferences) and pre-prints available in specialized repositories, as well as expanding the studies coverage by incorporating data from journals indexed in Scopus (non-WoS journals) and Emerging WoS journals, which do not have an impact index (Emerging Sources Citation Index, ESCI), but allow recovering more studies developed in the periphery and semi-periphery of global knowledge production.
Regarding future research lines, it is relevant to advance brain drain studies on less studied geographical areas. Studying less researched locations, researchers can offer new light about the effects of this phenomenon on the sustainability of those countries and territories. Other study areas include the destination country concept incorporation and brain circulation optics, the attraction and permanence forces in those destinations, the mobility motivations, and the subsequent effects, both personal and national. The social researcher’s role in the brain drain is also interesting for the social sustainability effects, a product of their contributions to social sciences. Finally, the SARS CoV 2 pandemic scenario increases the tension due to the health personnel brain drain, making them another interest group to be studied today, which may even be of interest in national security and geopolitics.