If some immigrants return without pensions, then the third term Bq is also positive
and the gain is evidently bigger. In practice, rules governing the portability of social
security rights accrued by virtue of taxes paid while working as a temporary immigrant
are complex and differ in the UK, for example, for EU and non-EU citizens but those
rules together with rates of return migration need to be understood to appreciate the
long-run fiscal impact of migration. More broadly, if we think of benefits enjoyed in the
final period of life as encompassing not only pensions but benefits received in kind,
especially health services, then it is clear that a substantial portion of these will not be
internationally portable. ‘Not all social benefits are fully transferable, making return
beneficial for the host country’ (Organisation for Economic Cooperation and
Development, 2013, p. 140).