Let’s be clear from the off. There are several things that are often smushed together when it comes to immigration policy. One of these is the aspiration to reduce net migration from the hundreds-of-thousands to the tens-of-thousands. Another of these is the Coalition’s cap on certain types of migrant worker. Another is the big bundle of policies designed to restrict other types of immigration. To say something about each of these in turn:

  • The aspiration to reduce net migration from the hundreds of thousands to the tens of thousands is mostly just that – an aspiration. Insofar as it counts as a target, it’s a Conservative target. The Liberal Democrats haven’t signed up to it. It’s not strictly a Government policy.
  • The Coalition has, however, introduced some caps on the level of economic migration. The Tier 1 (Exceptional Talent) visa, for world leaders in the arts and sciences, was first introduced and then capped at 1,000 a year. The number of Tier 2 (General) visas has been capped at 20,700. These are effectively for skilled, graduate-level jobs.
  • The bundle of other policies to restrict immigration is too large to properly summarise here, but the main point is that none of them are true caps. They include everything from tougher language rules for migrant students, designed to crack down on bogus applications as well as to simply reduce the number of student visas being handed out, to greater monetary requirements for incoming spouses. Sometimes numbers have been attached to these policies – when May first announced the student visa restrictions, she suggested that they would reduce net migration by 70,000-80,000 a year – but these have always been forecasts, not caps.

So, how is all this working out for the Conservatives? It depends what you mean by “working out”. When it comes to raw politics, the answer is less than heartening. Since David Cameron first announced his “tens of thousands” goal, at the start of 2010, the Tories’ poll lead on immigration has been slowly whittled down, almost to naught:

140711 immigration graph

Which could, of course, be a function of simply being in Government – and having those immigration policies tested against the newspaper headlines every day – but it’s certainly not what was desired.

But how have the Tories’ immigration policies worked on their own terms – in cutting numbers? Let’s consider the three areas I highlighted above, in reverse order this time:

  • Such a big bundle of policies is hard to judge in summary. Reductions in some parts (e.g. the number or Tier 4 student visas has declined from 341,305 in 2009 to 218,773 last year) have been counteracted by increases and abuses in others (e.g. as the Telegraph notes today, the number of “entrepreneur” visas has gone from 118 in 2009 to almost 10,000 now). But the overall picture is that net migration from non-EU countries has fallen by about 70,000 since the Government came to power, to its lowest levels since 1998.
  • Another one that’s hard to judge, mainly because it’s difficult to say whether the caps have had a shuddering effect or are largely pointless. For instance, the 20,700 cap on Tier 2 visas has never actually been reached. Just under 10,000 were issued in 2010, and the figure is roughly the same now. This could be because the restrictions attached to it are so draconian that it puts off potential entrants – and there is some anecdotal evidence to that effect – or it could be that the cap is so high that it isn’t really capping anything. It’s also worth noting that other forms of economic migration, such as moving from a foreign to a British branch of a company, haven’t really been restricted.
  • This one is a little easier. Originally, long-term net migration fell from around 256,000 in 2010 to 177,000 in 2012. But that number has since increased to 212,000. This an increase driven mostly by EU migration, which is largely out of the Government’s hands. An extra 40,000 people immigrated from the EU in the year ending last December. The goal of reducing net migration to the tens of thousands looks a long way off.

This is the great paradox that has befallen David Cameron. By trying to sound tough on immigration he’s set himself a benchmark that’s too tough to achieve – at least by 2015. The net migration figure has always been a hostage to things the Government can’t control, including EU immigration, which accounts for almost 40 per cent of all immigration, and British emigration.

So how will the Prime Minister escape this self-inflicted trap? Not by letting go of the “tens of thousands” aspiration, I’ll bet. Downing Street won’t want to do that in the face of both voter concern about immigration and the rise of UKIP, so they’ll just carry on trying to cut numbers. This will involve, as it already has, talk of imposing controls on EU migration. It will involve, as it already has, a tightening of the current restrictions.

Which brings us to the final – and most important – way of assessing the Government’s immigration policies: by what they have done for the country. Have they harmed the economy? Have they done anything for social cohesion? Just what have they achieved in sum?

And this is where the story breaks down. It’s not that there are no numbers on this sort of thing: the Office for Budget Responsibility has, for instance, tried to estimate the effect of immigration cuts on the public finances. It’s more that the numbers are patchy, at best, and outright wrong, at worst. There are a million variables that matter when it comes to immigration. We only have a handful of ‘em.

Really, the reason I’m writing all of this is because of a debate that took place on ConHome last week. On one side was Sir Andrew Green, writing against the Higher Education Policy Institute’s suggestion that students should be removed from the net migration figures. On the other, in the comments section to Sir Andrew’s post, was HEPI’s own Nick Hillman. By way of a disclosure, I’ve argued before – in The Spectator – that students should be taken out of net migration.

This debate is probably wearily familiar to you. Folk like me point to the piles of cash that British universities are missing out on. Folk like Sir Andrew point to the persistence of bogus colleges and fake courses. But something that isn’t said enough is this: the information that both sides rely on is terribly incomplete.

For instance, did you know that it was only in 2012 that the Office for National Statistics started asking departing migrants what their original reason for immigration was? Until then, we knew whether incoming migrants were arriving for study. But we didn’t know whether outgoing migrants had first come over for study. So a comparison couldn’t be made between the numbers arriving and the numbers leaving. The information wasn’t there.

And, even now, it’s still difficult to make that comparison. As the Migration Observatory explains, the ONS’s numbers come from a survey – the International Passenger Survey – and are subject to wild margins of error. They also jar with what work the Home Office has done on this subject.

It was very telling that, in their debate, Sir Andrew and Hillman alighted on single branch of agreement. As Hillman put it in a separate blog post:

“If Sir Andrew is saying we need better information on student migrants, their impact and people’s views about them, he is right. Some individual universities have had a go at assessing the full impact of international students on their geographical areas but there has been no national assessment that has resonated loudly around Whitehall…

…An excellent way to improve the evidence base on international students would be to commission the [Migration Advisory Committee] to conduct a full review of the costs and benefits to the UK of international students. It would take a while to do properly, as the MAC tends to be rigorous, but the rather painful debates on international students have been going for a long time already and they show few signs of abating.”

This isn’t the standard reach-for-a-review response that prevails in Westminster. It actually matters. Like I said, the Conservative leadership are almost certainly going to stick by their immigration policies. There are signs that Labour are coming round to them too. Immigration restrictions are here to stay – but, at the moment, they’re largely based on guesswork.