4. Scientists on the move

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Scientists who undertake research abroad and return to the economy in which they first published contribute to raising the overall quality of domestic research by 20% on average.

Scientist mobility facilitates the circulation of scientific knowledge. One way to track the mobility of scientists is to trace changes in institutional affiliation over their list of publications in scholarly journals. This approach shows that brain circulation (churn) is far more important than brain gain/drain (net flows). The nine largest international bilateral flows of scientists over the period 2006-2016 involved exchanges with the United States. Of the top 40 connections, this country was a net beneficiary in 14 cases, followed by the United Kingdom with 6 and China with 5.

In 2016, authors based in Luxembourg and Switzerland experienced the highest mobility rates within the OECD. For the median economy, 95% of scientists in 2016 were already based there at the time of their previous publication. Mobility patterns vary across economies; for example, in Israel and Italy, a majority of inflows are returnees originally affiliated to an institution in the country. In Switzerland, the majority of researchers with an international mobility record represented new inflows.

With few exceptions, individuals not changing economy affiliations (stayers) are more likely to publish in journals of lower “prestige”. Outflows tend to be associated with higher rated publications than their staying or returning counterparts, although in the case of the United States, outflows display lower journal scores. The scores of inflows are still higher than those for stayers in this country, pointing to a continued ability to attract top scientists.

Definitions

Scientific authors are listed in the Scopus database of peer-reviewed scientific publications and identified by a unique author ID assigned by Elsevier. International mobility is inferred from authors with at least two publications over the reference period and is based on changes in institutional affiliation and sequence of publications. Stayers maintain the same economy of affiliation over the reference period. Among inflows, returnees are authors observed to move to an economy in which they were first affiliated, in contrast to new inflows. Outflows are measured in terms of the affiliation at the beginning of the reference period.

The Scimago Journal Rank (SJR) score is a measure of scientific influence of scholarly journals that accounts for both the number of citations received by a journal and the importance or prestige of the journals where the citations are made (González-Pereira et al., 2010).

Measurability

Bibliometric indicators provide a complementary picture of global researcher mobility. First developed by Elsevier (2011), these indicators are experimental and require careful interpretation (Moed et al., 2013). Mobility is less accurately measured or missing for less prolific authors and for those who move from and into non-academic roles. Affiliations may be recorded with a lag and may not reflect where the research took place. In this version, authors with multiple affiliations are assigned a “main economy” per document, with one economy picked at random in the case of equal weights. More importantly, failure to assign author IDs consistently can distort mobility estimates by understating mobility when an individual has multiple IDs, or overstating it for individuals with common names. The open researcher and contributor ID (ORCID) promotes the use of unique identifiers linkable to an individual’s research output. An OECD analysis of the international scientist mobility network and its main drivers is available (Appelt et al., 2015).