Just how big will the big slump be?

The world may be heading for its worst recession in a quarter of a century - if it's lucky.

A steep slump looks likely as the credit squeeze crunches economies from the US to Singapore and panic engulfs global financial markets.

"It's certainly going to be the worst since the 1980s," says Bradford DeLong, an economics professor at the University of California at Berkeley who worked at the US Treasury Department from 1993 to 1995. "The hope is that it won't become the worst unemployment business cycle since the Great Depression."