PEG Ratio Unreliable as a Market-Wide Indicator

A study examined whether the price-earnings-to-earnings-growth (PEG) ratio can be used as a market timing tool.

The PEG ratio is a popular valuation metric used by investors to assess a stock’s price relative to its projected earnings growth. The researchers wanted to find out if the measure provides meaningful insights for broad market trends.

To investigate this, they analyzed historical PEG data for the S&P 500 index from 1985 to 2020, using Yardeni Research’s price-earnings (P/E) ratio and its forward earnings growth estimates. They tested the effectiveness of a market-timing strategy based on PEG thresholds, specifically whether buying when the PEG ratio is below 1.0 and selling when it surpasses 1.0 would yield consistent returns. Stocks trading at a PEG ratio below 1.0 are seen as opportunities by investors.

The researchers found that PEG ratios falling below 1.0 were rare over the study period. Ratios below 1.0 appeared briefly in the 1980s and only a few times in the 2000s and 2010s. A trading strategy based on the PEG ratio showed inconsistent results, especially after the year 2000. Returns associated with different PEG levels fluctuated significantly across decades, highlighting the strategy’s volatility.

The PEG ratio is useful for evaluating individual stocks, but its effectiveness in predicting overall market movements is questionable and it is unreliable as a stand-alone tool for market timing. This highlights the need for a broader analytical approach that incorporates other fundamental and macroeconomic factors.

Source: “Is the PEG Ratio a Reliable Market-Timing Tool?” by Derek Horstmeyer, Gopika Patel and Michael (Joonhyuk) Lee; CFA Institute Enterprising Investor blog, February 25, 2025.