Less of a bubble than a market rally

It has been more than five years since Alan Greenspan raised his infamous concern about 'irrational exuberance'' in the US stock market. Yet economic policy makers are no closer to figuring out when market rallies are bubbles and when they're for real. Take South Korea, an economy that's surprising even the optimists with its strong growth and robust asset markets. Ratings agencies, too, are impressed by its performance. Moody's Investors Service yesterday raised its sovereign debt rating two notches to A3. What heartens Moody's, which cited solid growth, shrinking foreign debt and prog...