Bernstein's view, known as the "Paradox of Wealth", is this: in early agrarian societies the cost of capital was high as the rich farmer could lend his grain at a very high rate of interest. For example, a bushel of wheat was paid twice over at harvest time, for a 100 percent return in less than a year.
As a society becomes more productive, wealth slowly spreads among those with grain, domesticated animals and money to spare, and capital becomes more plentiful.
"As societies get richer, the supply and demand equation shifts in favor of capital's consumers," he writes in a paper.
Based on energy consumption and cost of capital, Bernstein estimates a theoretical real investment return of 125 percent in prehistoric periods.
In ancient Mesopotamia and Greece's more advanced societies, interest rates fell to low double-digit levels; by the height of the Roman Republic and Empire, prime interest rates hit as low as 4 percent. Today, it is just 2 percent, he says.
"Both theory and long-run empirical data support the notion that economic growth lowers security returns; such is the price of living in an increasingly prosperous, safe, healthy, and intellectually gratifying world," Bernstein writes.