Before leaving representativeness, let us consider one more example showing that although financial professionals may recognize regression to the mean, they not apply it properly. Below is an excerpt from an interview that appeared in the August 18, 1997 issue of Fortune magazine, with global strategist Barton Biggs of Morgan Stanley and senior investment adviser Robert Farrell of Merrill Lynch (Armour, 1997). This interview occurred after two-and-one-half years of spectacular stock market returns. I have divided the excerpt into two parts. The first part sets the stage for a discussion about regression to the mean, and also for an issue that comes up in chapter 5 (on skewed confidence intervals). Here is the first part of the excerpt:
Biggs: My view is that we’re at the very tag end of a super bull market. That means the prudent person who’s thinking ahead toward retirement should assume that over the next five to ten years the total return from his equity portfolio is going to be in the 5 %- to 6%-a-year range.
Fortune: NOT THE 15% TO 20% WE’VE COME TO LOVE AND EXPECT?
Biggs: Right. It’s very late in the game.
Farrell: Trouble is, it’s looked that way for a long time.
Biggs: Yes, but it’s never looked as much that way as it does right now
We will come back to the “late-in-the-game issue” a little later. For now, consider regression to the mean