Lies, damned lies and forecasts?

Hopi Sen has an excellent reminder on his blog of how much weight we ought to give to predictions from the IMF . As he puts it:

Back in July, the IMF thought US growth would be 1.7% in 2008, and 1.4% in 2009. The Eurozone would grow by 1.7% and 1.2% in the same time period, while for the UK the figures would be 1.8% and 1.7%. In Japan, growth would be evenly distributed with 1.5% growth in both years. Less than six months later, and the figures are all startlingly different. Japan goes from 1.5% to an economic decline of 0.3% and is expected to decline by another 2.6% in 2009. 2008 Eurozone growth drops from 1.7% to 1% and then to -2 in 2009. The UK goes to 0.7% and-2.8 while the US drops to 1.% growth in 2008 and a decline of 1.1% in 2009.