W hat will be the shape of the US economic downturn? In recent months, the debate among economists has shifted from whether the US will have a recession to how deep and how long it will be.

Will it be a V-shaped recession - short, shallow and followed by a rapid return to normal rates of growth? Will it be U-shaped, in which the initial downturn is followed by a protracted period of weak growth and a slow return to the trend rate? Or could it even be an L-shaped recession - with economic weakness lasting for many years, as in the US during the Great Depression or Japan in the 1990s?