Investing Over 10 Years: Stocks vs. Bonds

by: David Merkel, CFA

Recently Bill Rempel posed the following question to me:

Could you compare the total return of a 10-yr Treasury bought fresh and new anywhere from 1976-1980, and held to maturity (sending the coupons to cash) — to the total return from an equal-sized basket of stocks or residential real estate over the same time period? Please use “risk-adjusted returns” in the previous comment, re: returns on bonds. As a non-institutional investor who doesn’t care as much about the “mark to model” on any bonds I would hold, I would view double-digit Treasuries as free money, especially in light of long-term returns on stocks barely cracking the DD with divvies included …

He also made this recent post to further elucidate his views. So, let’s do a thought experiment. Suppose you knew where real interest rates and inflation would be ten years from now. How would that affect your investment policy?

The easy answer would be that you would know what to do with bonds. After all if rates are higher in the future, you would shorten your bond holdings to preserve your capital, and vice-versa if rates were lower.

But what do you do with your stocks? How is their performance impacted by future real interest rates and inflation rates? Before I answer that, let’s consider the difference between the yield of a bond, and its realized return from reinvesting the coupons. The following graph shows the coupon rate on a ten year Treasury note, and the realized return from investing the coupons at money market rates until the bond matured. The realized return is higher than the coupon when the average money market rate was higher than the coupon, and vice versa. But the difference is rarely very large. Most bond income comes from coupons.

Now, let’s consider how the ten year Treasury yield, inflation and real rates have varied over my study period, 1954-1997.

And look at how the ten year Treasury yield, the real rate of interest, and the inflation rate would change over the next ten years.

Looking at these graphs, you can guess that future equity returns are affected by changes in inflation and real interest rates, but here’s proof:

Or, another way of looking at it, future equity returns depend on future real interest rates and inflation rates. Note that bonds only beat stocks for ten-year investments beginning during the period 1964-1973, and not all of the time even then.

I ran a regression on the difference between ten-year stock returns and ten-year realized Treasury note returns, with the regressors being the current inflation and real interest rate, and the inflation and real interest rates 10 years from then. The R-squared was 57% (good in my opinion), and the coefficients were:

* Current inflation: +22%
* Current real interest rate: -12%
* Inflation 10 years from then: -121%
* Real interest rates 10 years from then: -46%

There was some autocorrelation of the residuals, indicating that periods of under- and out-performance of equities over bonds tends to persist:

All were statistically significant at a 95% two-sided level. What the regression tells us is that of the four variables considered, the most important one is future inflation rates. If future inflation rises, the value of future cash flow declines.

It gets even worse if the Federal Reserve tries to squeeze out inflation by raising real interest rates high enough to overcome the inflation. Oddly, higher current inflation is a modest plus — maybe that indicates pricing power? Perhaps it is useful to think of equities as ultra-long bonds, with rising coupons. Rising rates would hurt those considerably.


1. Note that it was a bullish period, and that stocks did not lose nominal money over a ten-year period to any appreciable extent.
2. Stocks almost always beat bonds over a ten-year period, except when inflation and real interest rates 10 years from now are high.
3. Investing in stocks during low interest rate environments can be hazardous to your wealth.
4. Watch for inflation pressures to protect your portfolio. Stocks get hurt worse than bonds from rising inflation.
5. Inflation and real rate cycles tend to persist, so when you see a change, be willing to act. Buy stocks when inflation is cresting, and buy short-term bonds when inflation is rising.