IN THE year to September “net” migration to Britain was around 300,000. The figure is calculated by subtracting the number of people leaving the country from the number arriving. The government has wanted to cut the net-migration figure to the “tens of thousands” since the Conservatives took power in 2010, a target that has grown only more urgent after the Brexit vote, which it interprets as a vote to reduce immigration. On a legalistic reading, it is therefore targeting net migration of, at most, 99,999 (but preferably far lower). Yet without big changes to British society and the economy, meeting the target is near impossible. Why?

The British government can probably rely on net emigration of British nationals of about 50,000 per year. As a result, net migration of foreign nationals could hit around 150,000 a year, and the government could still hit its target. There are three main ways that people enter Britain: to work, to study and to be part of a family. It looks hard for the British government to cut net migration of foreign family members, which numbers around 70,000 a year once you include refugees. Recent court rulings have indicated that the British government’s no-nonsense rules on family reunifications, which impose tough income requirements on visa sponsors, probably could not be made tighter.

So even before dealing with the other two sources of net migration (work and study) the British government is already halfway towards 150,000. Net migration of foreign students is around 100,000. Some argue that students should be excluded from the figures but the government has rejected this suggestion: after all, like any other people students use public transport and the NHS. Imagine instead that the government cut it in half. That would damage a lucrative industry, and the quality of British research would suffer. But it would bring net migration of students down to around 50,000. With net migration then sitting at around 120,000, the government would turn to workers. It could abolish all unskilled migration from outside the EU. That would probably cut overall net migration by zero: there is almost no migration of unskilled workers from outside the EU. The government could however completely cut unskilled migration from the EU. That would reduce the total by around 50,000 a year.

That leaves just skilled migration, from both inside and outside the EU. That currently stands at about 60,000-70,000 a year. Were the government to allow all that, it would still overshoot its target, perhaps by 30,000-40,000 people. So it would probably have to cut skilled migration too. For an economy which is likely to be buffeted by changing trade relationships as it leaves the EU, cutting off the supply of skilled workers doesn’t make very much sense. Which is why pulling net migration below 100,000 is likely to remain a pipe dream.