The reason stocks are a decent inflation hedge is because corporate earnings grow faster when inflation is higher, and grow more slowly when inflation is lower, according to Richard Warr, a finance professor at North Carolina State University. Consider the growth rate of corporate earnings over all 10-year periods since 1871, according to data compiled by Yale University finance professor (and Nobel laureate) Robert Shiller. The volatility of those growth rates was 21% less on an inflation-adjusted basis than it was on a nominal basis, which Prof. Warr says is a good indication of the extent to which equities are able to hedge inflation.
To be sure, Prof. Warr adds, higher inflation does reduce the present value of the otherwise higher future earnings. But these two effects should more or less cancel each other out over time.
Prof. Warr acknowledges that, over shorter periods of a year or two, stocks often suffer when inflation heats up. His research suggests that is because many investors are guilty of what economists refer to as “inflation illusion.” That is, they focus only on the reduction in the present value of future earnings to which inflation leads, while ignoring the tendency for nominal earnings to grow faster when inflation is higher. So when inflation spikes upward, they sell stocks.
Since the inflation illusion is irrational, it is difficult to predict whether investors will be guilty of it the next time inflation heats up. But Prof. Warr says that if they do and their selling causes the stock market to drop, investors should treat it as a buying opportunity."