ABSTRACT
While migration is a complex and difficult subject, the one thing of which researchers in Britain have been unable to complain in recent years is a lack of relevant data. More specifically, since 1975, information has been made available from the National Health Service (NHS) central register on gross bilateral, or pairwise, flows each year between the standard planning regions. These data are derived from people’s changes of doctor as they move from one locality to another, and thus cover virtually the whole population of those who migrate.
