Nigel Harris is Professor Emeritus of the economics of the city at University College London. Among his books are Thinking the Unthinkable: the myth of immigration control (2002), and The Return of Cosmopolitan Capital: globalisation, the state and war (2003). This is an extract from The Economic Case for an Open Migration Policy, for the Migration Dialogue of the European Policy Centre and the King Baudouin Foundation, Brussels, in June 2003.