Are P/E Ratios Worth Anything?

I’m currently reading Ken Fisher’s The Only Three Questions That Count – Investing by Knowing What Others Don’t. I’m only on Chapter 1, but have come across something I want to share with you about Price-Earnings Ratios (better known as the P/E Ratio). According to Fisher, P/E ratios are not a very good indicator of where the market is headed. To come to this conclusion, Fisher analyzed 134 year’s worth of P/E ratios and market performance. He found:

When you note the P/E ratios for the past 134 years along with the subsequent market return, some empirical truths emerge. Most startling? Most double-digit calendar-year stock market diclines – the monster drops everyone fears – occurred when P/Es were below 20, not when they were very high. Most were acutally when the P/E was below average. In the past 134 years, there were 19 times the market’s total return was negative more than 10 percent. Theirteen times – 68% of those most negative years – were on the middle to low end of the P/E range, 16.5 being the middle of the bell curve.

NOTE: It is important to note that of the 134 years, only 17 of them had P/E ratios above 20. So, it shouldn’t be surprising that most of the market’s big drops came when the P/E was below 20.

Before I go much further, I want to make sure we understand what a P/E Ratio is.

What is a P/E Ratio?

A P/E Ratio is a stock’s price per share divided by the earnings per share. So, if a stock is trading for $75 per share and it earned $3.50 per share, its P/E Ratio is 21.4 (75 ÷ 3.5 = 21.428571). This tells us that for this stock, we are paying $21.43 for each $1 of earnings. So, is a P/E ratio of 21.43 too high for this stock or too low? Good question! A lot of it depends on what kind of company this is and what industry it is in. In other words, you can’t just look at a P/E of 21.43 and say that this stock is overvalued. This is the point that Fisher makes in chapter 1 of his book.

Another way to look at the P/E Ratio

The earnings yield is simply the P/E Ratio turned upside down. To get the earnings yield, you simply divide the per share earnings by the price per share (Earnings Yield = E/P). Or, you can simply take the reciprocal of the P/E Ratio to get the earnings yield. The earnings yield makes it easier to compare a stock’s valuation with the yield you can recieve on fixed income investments. Now keep in mind that we still don’t have an apples-to-apples comparison because earnings can change on a whim (aren’t guaranteed), while government bonds are backed by the United States government. Also, there are both current earnings and forward-looking earnings. Current earnings are no guarantee of future earnings and forward-looking earnings are based on anayst’s estimates, which we all know are seldom accurate.

NOTE: Don’t confuse the earnings yield with the dividend yield, which is the dividends per share divided by the price-per-share. Dividends represent earnings that are coming back to you (as long as the company can afford to pay them).

Back to our example

In the example used above, we found the P/E for the stock to be 21.43. Taking the reciprocal (also called the inverse) of 21.43, we get an earnings yield of 4.67% (1 ÷ 21.43 = .046664). Now we can more easily compare the relative attractiveness of stocks to bonds and money market accounts, keeping in mind the risks involved with stocks. Of course, this isn’t the only thing to keep in mind when investing, but it can be a helpful tool.

11 thoughts on “Are P/E Ratios Worth Anything?”

  1. This is horrible information. P/E ratios are not intended to predict market collapses. They are useful when comparing similar companies/industries at the same point in time.

  2. To put it another way this is similar to saying that a company with shares of stock selling at $10 a share is worth 5 times the value of a company sell shares for $2 a share. Share price is meaningless in this context.

    The total value of the company would depend on the number of shares and the price.


    “One reason to calculate P/Es is for investors to compare the value of stocks, one stock with another. If one stock has a P/E twice that of another stock, it is probably a less attractive investment. But comparisons between industries, between countries, and between time periods may be dangerous. To have faith in a comparison of P/E ratios, one should compare comparable stocks.”

  4. I think you both have a valid point:

    1)Average P/E for the market can give you a feel for how the overall market is valued compared with other times in history.

    2)P/E is an excellent tool to compare the value of two stocks of companies that do similar things (same/similar industry).

    Let’s leave all the tools in the toolbox!

  5. some i should help me out with this:it this formula correct:the inverse of P/E ratio is equal to the Cost of Capital?

  6. Interesting information. I work for Fisher Investments, and there’s a bit more about Ken Fisher in his bio on his book website; including his background as well as an outline of other books he’s written. His two latest books, The Only Three Questions that Count and The Ten Roads to Riches were both NYT and WSJ bestsellers

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