Last night Standard and Poor stripped Britain of its AAA credit rating, down two notches to AA. So did Fitch Ratings, which downgraded the UK from AA+ to AA.

Politically, it's the Fitch rating which is worth taking a close look at. In its reasoning, the agency says:

"Medium-term growth will also likely be weaker due to less favourable terms for exports to the EU, lower immigration and a reduction in foreign direct investment."

But hold on a minute, wasn't immigration supposed to be damaging to the British economy and a drain on our services? After all, Migration Watch, the heritage brand of anti-immigration groups, put out a report before the referendum claiming migrants are ruining the economy.

"Overall, migrants in the UK have been, and continue to be, a net fiscal cost to the UK Exchequer," it said. "Immigration has not been shown to have any significant impact, either positive or negative, on GDP per capita, a key measure of economic performance. There is therefore, no economic case for mass immigration on the present scale."

This goes against all the academic literature on the subject – study after study by respected researchers. But it, and messages like it, worked. Voters believe immigration damages the UK economy. They believe the costs of EU workers coming to Britain "outweigh the benefits", as the chart below shows.

So they voted out. And days later a credit rating agency – which has no dog in the political fight – makes it clear that the academic research is correct and the tabloid editors and anti-immigrant groups are wrong. Reductions in immigration damage the economy.

Expect more drops in the credit ratings to come, not just because of the drying up of international investment and the lack of stability, but because of the expectation that we're about to start reducing immigration.

Ian Dunt is the editor of

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