We just wrote a piece for Forbes on financial bubbles in the lab. Punchline: investors initially underreact to fundamentals, then they overreact, and eventually prices correct. But how common are crashes? Ben has some interesting thoughts, but the results are limited to the US market. Now, one of my favorite academic authors — Prof. Bill Goetzmann — has a new paper that speaks to understand the frequency and dynamics of “bubbles” throughout history and across multiple global markets (i.e., the real-world lab!).
Here is the abridged abstract:
… In this paper I examine the frequency of large, sudden increases in market value in a broad panel data of world equity markets extending from the beginning of the 20th century…The chances that a market gave back it gains following a doubling in value are about 10%. In simple terms, bubbles are booms that went bad. Not all booms are bad.
The table below highlights some interesting points. The biggest point is that following a doubling of prices, the probability over the next 5 years of another double is 26.39%, but the probability of losing 50% is 15.28%. So big price movements occurring over short periods (i.e., “bubbles”) are more likely to continue, not burst.
A few key learnings points that I gleamed from the paper:
- Bubbles are rare, empirically. But bubble chatter is common.
- Most large increases in prices are not followed by huge crashes. In fact, the opposite is true: larger price increases are more likely to be followed by large price increases, relative to a a large price decrease (i.e., a crash).
- Focusing on avoiding bubbles can come at a great expense — crash protection may cause an investor to forego the equity risk premium. This analysis layers on a higher burden of proof for market timing and/or downside protection models.
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