Estimating downside risk

I have warned about excessive valuation before (see 2025 Outlook: Cautious But Not Bearish). The S&P 500 is trading at a forward P/E of 22, which is elevated by historical standards. On one hand, valuation isn’t highly predictive of returns over a one-year horizon. On the other hand, elevated P/E ratios lead to lower returns over a five-year time horizon.
 

 

In other words, valuations don’t matter until they matter. As investors look ahead into 2025 against a backdrop of a high P/E market, one key question is: “What’s the downside risk in the event of a bear market?”
 

 

A giddy backdrop

Callum Thomas of Topdown Charts highlighted the frothy nature of the market today. IBES is known for its compilation of analyst earnings estimates. In addition to the well-known consensus FY1 and FY2 EPS estimates, IBES also publishes a long-term EPS growth estimate. As the accompanying chart shows, long-term growth estimates have reached the giddy levels similar to the dot-com bubble top.
 

 

The combination of elevated P/E valuation and extremes in earnings growth expectations makes the U.S. equity market vulnerable to a setback.
 

 

Sources of vulnerability

What could make stock prices fall? What if the Magnificent Seven growth were to slow?

 

To be sure, the stock market is rationally exuberant owing to the earnings growth of the Magnificent Seven compared to the rest of the 493 stocks in the S&P 500 (see Equity Return Expectations Under an Alien Invasion). On the other hand, this makes the market highly vulnerable to Magnificent Seven earnings disappointment. At a minimum, the gap in earnings growth expectations between the Magnificent Seven and the S&P 493 is expected narrow in 2025.

 

 

In addition, the stock market isn’t cheap even outside of the Magnificent Seven. Combined P/E ratios are equally elevated outside of TMT (Technology-Media-Telecom).

 


 

From a top-down perspective, the emerging divergence between the U.S. Economic Surprise Index, which measures whether economic statistics are beating or missing expectations, and the 10-year Treasury yield is worrisome.

 

The divergence is especially concerning as the inflation expectation trade is heating up.
 

 

If inflation expectations rise and push up yields, it would put downward pressure on P/E ratios.
 

 

Estimating downside risk

As the Magnificent Seven is a source of major vulnerability for the S&P 500, here is one way of estimating downside risk. An analysis of the limited history of changes in peak and trough P/E ratios shows that the median tech P/Es fell from 29.5 to 13.1, which is over 50%, though that doesn’t represent actual price risk because earnings will rise during the bear market. Nevertheless, a ballpark estimate of price risk in technology stocks should the AI bubble burst would be about 50%.
 

 

As the Magnificent Seven represents about 32% of the weight of the S&P 500, this translates into about 15% downside risk for the overall index. The 15% downside is a minimum estimate, as the S&P 493 would likely decline as well. Assuming a lower beta in the S&P 493 during a price decline, we estimate bear market downside risk at 20–30% for the S&P 500.

 

 

Watching for bearish triggers

Despite my valuation concerns, I see no immediate bearish triggers for stock prices. High yield funding proxies, such as the junk bond spread plus a five-year Treasury yield, and actual junk bond yield levels (blue and red lines) are not showing signs of excessive funding stress. I consider junk bond funding a sensitive canary in the coalmine of equity fund costs, which needs to be closely monitored.
 

 

I am also keeping an eye on the Advance-Decline Line, which is showing a minor negative divergence against the S&P 500. Historically, A-D Line divergence have lasted for months before major tops of the market.
 

 

In conclusion, the U.S. equity is highly vulnerable because of overvaluation and excessive growth expectations, but valuation is not very predictive of returns over a one-year time horizon. I estimate downside risk on the S&P 500 in the 20–30% range in the event of a major bear market. Despite my concerns, I see no immediate bearish triggers for investors to adopt defensive positioning in their portfolios.