‘Only the higher-than-expected numbers of migrants coming to the UK under the post-Brexit migration regime adds materially to prospects for potential output growth over the coming five years relative to the assumptions that we made in March.’

That’s from the Office for Budget Responsibility’s (OBR) assessment accompanying the Autumn Statement. It’s a pretty striking line: the state’s official analyst of the public finances says that the only good thing to happen to the UK economy since March is higher immigration.