Investment manager and best-selling author Ken Fisher has a new book, Debunkery. His goal in the book is to refute common investment beliefs that he believes are wrong. His approach seems to be similar to ours in Retirement Watch. Fisher tries to look behind the beliefs and rules-of-thumb to the underlying data. Often, as we’ve found, the data don’t support the belief, or over time people forget the qualifications and assumptions that originally were part of the belief.
I haven’t read the book, but here’s an interesting review. The review’s main point is that Fisher does a good job of demolishing a lot of myths but makes poor arguments when addressing other myths. This reviewer hints that Fisher’s presentation is influenced by his business of managing stock portfolios for investors in separate accounts. Here’s a sample:
Let’s turn to chapter 26, “Low P/Es Mean Low Risk.” In it, Fisher states, “Using P/Es to forecast risk and return over any reasonable time period is about as useful as using an Ouija board.” Fisher is talking about P/E ratios based on 12-month trailing earnings, and in this narrow sense he is correct. When calculated in that manner, P/E ratios provide little useful information.
Fisher does not mention, however, the predictive power of normalized P/E ratios, popularized by Yale professor Robert Shiller, which use earnings averaged over the last 10 years. Those P/E ratios have been shown, by Shiller and others, to be reliably predictive of returns over long (e.g., 10-year) time horizons. That finding has been used, for example, by Michael Kitces to show that sustainable withdrawal rates can be increased by increasing equity allocations when markets are undervalued.
Fisher compounds that oversight when, in chapter 20, he writes, “There is absolutely no way – none – to predict stock market direction 7 or 10 years out unless you can somehow predict future stock supply shifts.”
The notion that stock prices are driven by the supply and demand of securities is one that Fisher advances several times in the book, notably in chapter 10. By contrast, I looked for a discussion of the role that a company’s free cash flow generation plays in determining its stock price and could not find one.