Retail maintains its iron stomach

The stock market is down significantly, but insofar as that market-reporting cliché the "wave of selling" is anywhere to be seen, it isn't coming from mom-and-pop investors.

By the numbers: As stocks plunged on Monday, more than twice as many Fidelity customers were buyers than sellers.

• “Customers are using the market volatility to add equities to their portfolio,” Fidelity’s Robert Beauregard told Yahoo Finance. 

At Vanguard, customers were even more sanguine, with less than 0.3% of retirement accounts making any trades at all in the past month.

One reason people rotate into stocks is when they pay out much more in dividends than a Treasury note does in interest payments.

• That's not normally the case. The dividend yield on the S&P 500 is generally lower than the yield on the 10-year Treasury note because investors expect to make money not only from stock dividends but also from price appreciation.

Earlier this week, however, the dividend yield on the S&P 500, at 2.09%, was more than 4 times the yield on the 10-year Treasury note. That easily marked an all-time high for the ratio.

• Be smart: There are limits to how informative this ratio can be. If 10-year bond yields head negative, for instance, as they have done in Germany and many other countries around the world, the ratio would first spike up to ∞ and would then go negative itself.

Why it matters: This ratio doesn't help you time the market — stocks can always fall further. But it's easy to see how investors in Treasury bonds might start worrying that their money is no longer working hard for them.

Go deeper: Don't panic about the stock market