Judging a recession is like walking down uneven stairs in the dark. We do not know how far down we must still go, only how far we have come. The end of the recession will not be clear until we are some way past it. So politicians should be wary of claiming to be able to see future positive trends.

This week, for the first time in months, there has been a steady trickle of good economic results from the US. Retail sales in January and February were 1.8 per cent higher than in December. Demand for durable goods rose by 3.4 per cent, and even house sales recovered slightly in February. Barack Obama sees “signs of progress”.