Everybody's trying to predict the next bubble. Reuters columnist James Saft says it may be emerging markets.

Emerging markets are very likely the next bubble, but don't let that stop you.

Emerging market shares are already expensive relative to developed market ones, but economic growth in places like China and India will continue to pull away, and investors will pay an increasing premium for that, especially if the ageing economic giants of the 20th century slip from their long term growth paths.

And in a process we've seen before with internet stocks and houses, big returns will attract big money, driving further rises and making it all seem very sensible, at least for a while.

The definition of "a while" is of course, as with all bubbles, the key question.