Bayesian Investor Blog

Up to two months ago, I was not too excited by the claims of a bubble in the Chinese stock market. Maybe the stocks that trade only in China were at bubble levels, but the ones that trade in the U.S. or Hong Kong still looked like mostly good investments.
Much has changed since then. On October 17, PetroChina rose 14.5%, more than doubling in about two months. That was a one day gain in market capitalization of almost $60 billion, and a two month gain of $247 billion (doubling the market capitalization). I’ve seen similar but less dramatic rises in smaller Chinese stocks that trade in the U.S., but less on the Hong Kong stock exchange.
By comparison, the largest rises in market capitalization that I’ve been able to find in the technology stock bubble of 1999-2000 were a $50 billion one day rise in Microsoft on December 15, 1999, and a $250 billion rise (doubling) in Cisco which took four months.
I’m not saying that Chinese stocks are clearly overvalued yet, and I’m still holding some stocks in smaller Chinese companies that I don’t feel much urgency about selling. But the unusually strong and long lasting Chinese economic expansion, combined with the unusually frothy action in the stock market, are what I’d expect to be causes and symptoms of a bubble.
Bubbles in the U.S. have peaked when real interest rates rise to higher than normal levels. The Chinese government is keeping real interest rates near zero, and seems to think it can keep nominal interest rates stable and reduce inflation. That would be an unusual accomplishment under most circumstances. When combined with a stock market bubble, I suspect it could only be accomplished with drastic restrictions on economic activity, which would involve instabilities that the Chinese government has been trying to avoid by stabilizing things such as interest rates.
Without a rise in interest rates or drastic restrictions of some sort, it’s hard to see what will stop the rise in Chinese stocks. So I’m guessing we’ll see a bigger bubble than the U.S. has experienced. It’s effects will likely extend well beyond China.