Buyers depend on valuation metrics to gauge whether or not a inventory is pretty priced. Amongst these, the PEG ratio is common for its capacity to regulate a inventory’s valuation based mostly on future earnings expectations. In contrast to the usual P/E ratio, which merely compares worth to present earnings, PEG incorporates progress projections. It’s merely an organization’s P/E ratio divided by its progress fee. Theoretically, this makes it a extra refined device for assessing whether or not a inventory is under- or overvalued.
However does the PEG ratio present significant insights for broad market developments? To seek out out, we analyzed historic PEG information for the S&P 500 (1985 to 2020) and examined its effectiveness as a buying and selling technique. We used Yardeni Analysis’s PE ratio and its estimates of ahead progress charges for a similar interval.
Exhibit 1. Mapping of the PEG ratio over time.
The standard knowledge is straightforward:
- PEG < 1.0 → The inventory is undervalued relative to its anticipated progress.
- PEG > 1.0 → The inventory is overvalued relative to its progress.
Many traders contemplate 1.0 to be a key threshold. If a inventory trades at a PEG under 1.0, it’s seen as a chance. Whether it is above 1.0, warning is suggested. If we use PEG to gage broad market developments, how typically do these “undervalued” alternatives seem, and do they sign sturdy returns?
Utilizing the S&P 500 information from 1985 to 2020 and ahead progress estimates from Yardeni Analysis, right here’s what we discovered:
- PEG < 1.0 is Uncommon:
- All through the Eighties, there have been a handful of months when the PEG ratio dipped under 1.0.
- Within the 2000s, this occurred solely 3 times.
- Within the 2010s, it occurred simply 5 instances.
- The PEG ratio nearly by no means gives constant shopping for alternatives at this threshold.
- PEG as Market Timing Software:
- We examined a technique the place an investor would purchase the S&P 500 when the PEG ratio was under 1.0 and promote when it moved above 1.
- Whereas this labored properly in some intervals—just like the Eighties—it was far much less efficient within the 2000s and past.
- Increasing the edge to 1.25 or 1.5 confirmed equally blended outcomes.
- Volatility is Excessive:
- The returns related to totally different PEG ranges diversified considerably throughout many years.
- What labored in a single interval typically failed in one other, making it tough to make use of the PEG ratio as a standalone market sign.
Desk 1.

Whereas the PEG ratio stays a useful gizmo for evaluating particular person shares, our evaluation means that making use of it as a market-wide sign is way much less dependable. Traditionally, alternatives to purchase when the PEG ratio falls under 1.0 have been uncommon, and the technique of buying and selling based mostly on PEG thresholds has yielded inconsistent outcomes, notably since 2000.
Whereas valuation metrics are priceless in funding decision-making, no single ratio ought to dictate market timing. As an alternative, traders ought to contemplate the PEG ratio as one piece of a broader analytical framework — complementing it with different basic and macroeconomic components to make well-rounded funding selections.
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