“Quantity has a quality of its own.” Whether or not Stalin ever said this about the Red Army, it is true of being out of work. Evidence is mounting that the long-term unemployed aren’t merely the short-term unemployed with the addition of a little waiting time. They are in a very different situation – and an alarming one at that.

Researchers in the US are setting the pace on this topic, because it is in America that a sharp and unique shift has occurred. Broad measures of unemployment reached high but not unprecedented levels during the recent great recession. Yet long-term unemployment (lasting more than six months) surged off the charts. It has been extremely rare for long-term unemployment to make up more than 20 per cent of US unemployment, but it was at 45 per cent during the depths of the recession. In the UK and eurozone, long-term unemployment is pervasive but that, alas, is not news.

As long as there is a recovery, why does this matter? A clue emerges when we look at two statistical relationships that are famous to econo-nerds like me: the Phillips curve and the Beveridge curve. (They are named after two greats of the London School of Economics, Bill Phillips and William Beveridge.)