Weekly Inflation Outlook: U.S. CPI Spike May Wane But That's Not The Full Picture

 | May 09, 2022 20:15

This article was written exclusively for Investing.com

Why did the stock market drop so violently on Thursday, after rallying so sharply on Wednesday?

Bond math can help answer this question. (In case you are new to this column…yes, I am a bond geek. And/or a derivatives geek. And/or, just a geek).

An equity security can be thought of as a perpetual bond that pays a dividend that increases over time and is discounted at a real interest rate. (Obviously, this construction runs into problems when we think about companies that don’t pay dividends, so we often look at earnings instead. In what follows, I use Bloomberg’s series for trailing 12-month EPS before extraordinary items.)

This is one reason that there is a clear relationship over time between equity multiples and interest rates; at high interest rates, distant earnings are worth less in current dollars, so current prices tend to be lower, while at low interest rates, those distant earnings are worth more and current prices tend to be higher.

[Side note: this doesn’t mean that the high multiples are correct because interest rates are so low, only that low interest rates explain high multiples. Your best guess about forward prices, if interest rates are artificially too low, needs to incorporate the notion that equilibrium interest rates are higher and therefore equilibrium multiples are lower. Then the question is merely about how long it takes to get to that equilibrium. This is why Minneapolis Fed President Neel Kashkari’s statement on Friday that long-term real interest rates are currently near neutral is as important as it is absurd. If long-term real interest rates are near neutral, then there is no mean-reversion to look for in equity multiples. But it’s a dumb statement.]

The chart below shows the S&P 500 index in blue. The interesting series is in red. In that series, I created a make-believe 30-year bond that has a coupon of the current S&P EPS, a principal amount that increases with CPI, and a yield to maturity of the current Earnings Yield plus the current 30Y TIPS yield. Think of it as a sort of TIPS bond that pays the current earnings of the stock market.

Both series are indexed to December 2002 as 100. You can see that this series does a decent job of tracking the stock market as a whole.