Byte # 12 –PEG Ratio: The Valuation Shortcut Investors Forget

Dear Reader,

Are you chasing growth? Don’t just stop at P/E—PEG gives you a clearer, forward‑looking view.

The PEG ratio—Price/Earnings to Growth—adds a forward-looking lens by factoring in expected earnings growth.

PEG Ratio = P/E Ratio ÷ Earnings Per Share Growth Rate

The concept was first introduced by Mario Farina in his 1969 book A Beginner’s Guide to Successful Investing in the Stock Market. However, it was Peter Lynch who popularized it in One Up on Wall Street (1989), famously stating that “the P/E ratio of any company that’s fairly priced will equal its growth rate,” implying that a PEG of 1 represents fair value.

Lynch used the PEG ratio to uncover growth stocks that were still attractively valued—an approach now known as Growth at a Reasonable Price (GARP).

For a detailed understanding refer to this article.

Why consider the PEG ratio?

When a stock appears “cheap” or “expensive” based on P/E alone, the PEG ratio adds an extra layer of insight by incorporating growth expectations.

For example, a company with a P/E of 20 might look pricey—until you see it’s growing earnings at 25%, giving it a PEG of 0.8 (below 1 = potentially undervalued) or or the reverse can be true if growth is weak.

Take a real-world example: Diageo (DEO)—a stock I discussed when explaining the P/E ratio in Byte #3. DEO’s trailing P/E is 16.16, and its forward P/E is 18.04. However, analysts project forward GAAP EPS growth of -7.92%, which makes its PEG effectively non-measurable.

Tip: If you’d like to filter for companies with a PEG under 1, the screener tool at finviz.com is free and offers an efficient way to screen stocks by multiple criteria.

Limitation: The accuracy of the PEG ratio depends on reliable growth forecasts, which can be uncertain or overly optimistic. It is best used alongside other metrics and not in isolation.

📈 Today’s Reality — Elevated PEG

The SPDR S&P 500 ETF (SPY) P/E is currently around 25–29× depending on whether you use trailing or forward estimates. Yet, earnings growth expectations have slowed to about 5–8% over the coming year.

That implies a PEG between 3.1 and 5.0, far above the “fair value” benchmark of 1.0.

✅ Bottom Line

Tread carefully—this elevated PEG reflects high market valuations combined with slower expected growth for the S&P 500 in 2025.

However, this doesn’t mean you can’t find opportunities. Many small- and mid-cap growth companies still trade with PEG ratios below 1.0, suggesting they may be more attractively valued relative to their growth prospects. Stock screeners like Finviz can help you discover them.

That’s it for today. If you found this useful, let me know—reply with your thoughts or forward this to someone who’d benefit!

Best,

Pooja