Surely the Great Depression couldn't happen again - or could it? One of the world's top economists gives us a sobering tour of the global economic crises of the last two years. Six Asian economies have experienced economic slumps; Russia, once military superpower, today economic midget, defaulted on its debt in 1998, driving Brazilian interest rates through the roof and terrifying the US bond market; and at Long-Term Capital Management, some of the world's brightest financiers thought they had the market licked only to find themselves in a jam with the makings of the over-leveraged positions that caused the 1929 crash. Paul Krugman recounts these events - pointing out that they raise questions for which economists may not have answers