The same logical conclusion can be reached by another route. Clearly, the capital markets and money-lending markets must compete for the same investors. In this world without uncertainty or risk, investors will decide to invest in one market or the other purely on the basis of expected return. The expected return in the money-lending markets, of course, is simply the interest rate. If the return in the capital markets became either higher or lower than that interest rate, then competition would create either an influx or outflux of investors in the capital markets, until equilibrium was restored between the two rates of return.

Our conclusion, of course, assumes that selling prices and costs can be perfectly assessed in advance by producers. Normally, elements of risk and uncertainty also affect the return to investors, and these will necessitate later adjustments to our analysis. It is clear, however, that investors' earnings—like all free-market prices, wages, rents, and interest rates—are determined by the natural law of the marketplace, and not by the arbitrary desires of the individual investor.