Finally, a truly depressing dynamic is taking hold in an ever richer world. Without getting too deeply into the macroeconomic weeds, as societies become wealthier, the amount of available investment capital grows faster than the amount of investing opportunities, and so the expected rate of return falls. In the beginning of human finance, ancient societies existed on the edge of subsistence, and so had little capital to spare. This drove interest rates as high as 30 percent.
