INSIGHTS | POLICY FORUM | HUMAN MIGRATIONS
promote effective intra-EU mobility, it needs to address the selection
issue and to support research environments, like European Research
Council hubs, that will induce the best researchers to choose the EU
for their mobility destination. Mobility support policies should target
early-stage Ph.D. students, as researchers with mobility experience
within Europe as Ph.D. students are more likely to remain internationally mobile within Europe post-Ph.D.
1. S. Kahn, M. MacGarvie, Rev. Econ. Stat.98, 397 (2016).
2. R.Veugelers, L.Van Bouwel, Res. Higher Educ. 56,360(2015).
3. L.Van Bouwel, R.Veugelers,in The Mobility of Students and the Highly Skilled,
M. Gérard, S. Uebelmesser, Eds. (MI T Press, Cambridge, MA, 2014), pp. 57–81.
Mismatched supply and demand
Kirk B. Doran8
Immigration provides opportunities to increase knowledge produc-
tion. But this depends on an increased demand for knowledge and
on immigrants expanding the supply of skills not otherwise available.
Unfortunately, this is not always the case. The first problem is univer-
sity-sector demand: If universities do not take advantage of a supply
increase by expanding faculty lines, new scientists can crowd out
current ones, with little change in knowledge. This happened around
1991 when >1000 Soviet-trained mathematicians emigrated, many
interacting with Western scientists for the first time. We learned the
effect of this shock by comparing subfields of U.S. mathematics that
the Soviets specialized in with those they knew nothing about (1).
U.S. institutions eagerly hired Soviets with the best curricula vitae,
especially midcareer mathematicians who had already excelled. But
without an expansion in faculty slots, the only slots available were
not those already taken by inferior tenured mathematicians, but
rather, slots that would have been taken by newly minted Ph.D.’s. Be-
cause young scientists have more years of productivity ahead of them
than do older ones, this proved disappointing: The new knowledge
produced by Soviet émigrés was at best on par with the knowledge
that would have been produced by the young mathematicians who
lost or never got positions or who went to inferior research jobs.
Average output of the most-affected American mathematicians
declined by about one-third. The second problem is supply in the
for-profit sector: If the U.S. H-1B visa program brings individuals
with skills already common in the United States, then the potential
for the firms that hire them to produce more knowledge than they
otherwise would have is limited. We compared firms that randomly
received access to H-1B visa immigrants to those that randomly did
not (2). The supply of workers with similar skills was sufficiently
prevalent that firms that missed out on hiring H-1B immigrants were
able to quickly hire someone else. At the firms that hired them, the
median H-1B visa employee crowded out approximately 1.5 other em-
ployees, with no increase in the firms’ patenting or patent citations
in subsequent years.
1. G. J. Borjas, K. B. Doran, Q. J. Econ. 127, 1143 (2012).
2. K. Doran, A. Gelber, A. Isen, “The effects of high-skilled immigration policy on firms: Evidence
from H-1B visa lotteries” (NBER working paper no. w20668, National Bureau of Economic
Research, Cambridge, MA, 2014).
Migration of ideas: China and U.S.
Migration of ideas comes not only from permanent migrants but also
from temporary migrants, such as international students, conference
attendees, and visitors at foreign laboratories and centers. Given that
collaborations generally arise from personal connections (1), it is
hard to imagine internationally coauthored research expanding absent researcher mobility. Ties between U.S. and Chinese researchers
exemplify how migration advances knowledge and benefits source
and destination country. The United States is the top destination of
Chinese international students and postdocs, and China is the top
source of foreign students in the United States, and they contribute
to U.S. scientific productivity (2). Those who return to China tend to
outperform other Chinese researchers in terms of citations in international scientific journals (3). Homophily in citations suggests that