In the face of the current highly ebullient stock market, close watchers of valuation metrics are frequently dismissed as ignoring the prospect for accelerating GDP growth and lower corporate tax expense, but I will step onto that turf anyway. It may make me look foolish, as Warren Buffett recently played down concerns about the market’s valuation, even though his often-preferred metric in years past (total stock market value relative to annual GDP) is dangerously high, but that’s okay.

Here is a look at my preferred valuation metric; a variant of the P/E ratio that uses “peak earnings” (l;the highest level of corporate profits ever produced in a 12 month period) instead of trailing 12 month earnings (impacted solely by the current economic environment) or forward earnings estimates (usually overly optimistic). We’ll go back more than 50 years, not only to get an idea of historical trends, but also because that is the data I have.

When people ask me about my view of the market, I tend to give a tempered response because it is hard to argue that we should really get any earnings multiple expansion. After all, we now sit above 20 times “peak earnings” and that has only happened once in the last 55 years. As you can see, that one time (the dot-com bubble of the late 1990’s) is not exactly a time we probably want to emulate this time around.

It is important to note that high valuations do not guarantee poor future returns. There is a high correlation, but you can map out mathematical scenarios whereby P/E ratios mean-revert and stock prices don’t crater. Simply put, it requires extraordinary earnings growth that can more than offset a decline in P/E ratios (which we should expect if interest rates continue to increase). Right now the U.S. market is banking on this outcome, so earnings and interest rates are probably the most important things to watch in coming quarters and years when trying to gauge where the market might go from here.