Nigel Farage told the TV debate audience on Tuesday that, under his proposed immigration points system, more black people would be allowed into Britain. The following morning, when grilled by Piers Morgan, he said:

What I would like is us to return to post-war normality. For about 60 years, we had net migration into Britain between 30,000 and 50,000 people a year.

Now there could be a bit of a problem with this. It depends on how you define black but I’m guessing most of the people from sub-Saharan Africa would fall into that category. Last year, net migration from that region was 21,000. Allow for people coming from the Carribean and you’d already be around half way to Nigel’s target. If he’s said that more black people are going to come in, that doesn’t leave much room for anyone else.

Meanwhile Priti Patel has been promising Asian voters that, after Brexit, more people from India and Pakistan will be allowed in, thereby solving the curry crisis. That’s going to be even more tricky, though, because net migration from the Indian subcontinent was 35,000 last year. The only way both promises could be kept, while staying within Nigel’s target, would be to completely exclude anyone else. Australians, Americans, Europeans, Chinese? Sorry, no room!

It’s all very silly. A cursory glance at the immigration figures shows that these claims are incompatible. This is what comes from telling different groups of voters different stories about immigration. The wonderfully vague promise that Brexit means ‘controlling our borders’ works like Zac Goldsmith’s election leaflets; one group of voters is encouraged to believe it will make it easier for their relatives to come to the UK, while another is persuaded that it will roll migration figures back by two decades.

The claim that the UK doesn’t control its borders is also absurd. Last year, over 2,000 EU citizens were refused admission, along with 15,000 from outside the EU. That’s why there are thousands of people camping in France trying to get to the UK. If we didn’t control our borders, they would be over here.

But what the Leave campaigners mean is that, because of our EU treaty obligations, we are obliged to let EU citizens into the UK unless there is a very good reason, usually based on national security, to bar them. It is true that the UK government can’t put a limit on the number of EU migrants. The trouble with this argument, though, is that the UK government hasn’t even been able to limit immigration in the categories which are under its direct control.

It said it wanted to reduce net migration to under 100,000 but net migration from outside the EU is still double that. Or, to put it another way, Even if there had been no migration at all from the EU, the government would still have missed its migration target.

Chart via ONS.

As Migration Observatory explained in 2011, it was always very unlikely that this target would be met. There are international treaties which mean that restrictions to migration for work and family reasons can only go so far. Even if the UK left the EU it would still be bound by these agreements. The World Trade Organisation’s General Agreement on Trade in Services (GATS), for example, obliges the government to allow companies to transfer employees between countries. Because so many multinationals have large operations in the UK, this country has the second highest number of migrants on intracompany transfers in the OECD. Last year, they and their dependents numbered just short of 60,000. It is true that the UK currently allows more people via this route than the GATS agreement demands but restricting it too far would not go down well with employers. The same is true for all non-EU migration. The recent rise in numbers has mostly been due to migration for work, driven by employer demands.

Much is made by Leave campaigners of the Australian points system but the UK effectively has something similar for non-EU migration, which quite clearly hasn’t reduced by anywhere near the amount the government pretended it would. An even tougher migration policy, post Brexit, would almost certainly lead some companies to move their operations elsewhere. An HR director I was talking to recently told me that he had very good reasons for keeping his R&D operation in the UK but that if he couldn’t recruit from the EU or elsewhere, he would have to move it to somewhere in central Europe. There is no guarantee that all the jobs currently done by migrants would stay in the UK. If the migrants can’t come to the jobs, the jobs might go to them instead.

Migration is not a bug, it’s a feature. An international economy like Britain’s, containing one of the world’s major global cities, is bound to attract a lot of migrants. When compared to the size of its population, though, the UK’s migration flows are not especially high. They are similar to other large European economies and some way lower than those of Australia and Canada, the countries whose immigration systems the Leave campaigners say they want us to adopt.

Chart via OECD International Migration Outlook

A certain level of immigration, then, is a characteristic of mature economies everywhere. It is one of those things that comes with globalisation and world trade. That is why the government has found it so difficult to reduce even the non-EU migration under its direct control.

The likely impact of Brexit and the restriction of immigration from the EU is that the shortfall in skilled workers will simply be filled from elsewhere. The mix of migration would change but the totals probably wouldn’t. It may be, as Nigel Farage said, that more black people would come into the UK. It is very unlikely, though, that there would be much of a reduction in the overall number of migrants. Reducing net migration to under 100,000, let alone Mr Farage’s 50,000, would have a serious impact on businesses and universities. Turning off the labour supply of an international economy which has been built on the assumption of a certain level of immigration is bound to have severe economic consequences.

The UK in the 2010s is a very different country from the UK in 1990s. Let’s stop pretending it can go back to 1990s migration numbers. Net migration under 100,000 is just not going to happen, not unless we turn the British economy into such a basket-case that no-one wants to come here any more, and there can’t be many, even among the most fanatical Brexit supporters, who would want that.

Most of the Leave campaign’s claims have now been well and truly trashed. Immigration is their trump card. It’s time to tear that one up and throw it in the bin too.