This document discusses the differences between periods of economic and market conditions. It notes that in the 1970s, inflation-adjusted returns hit -75%, while the 1980s-90s saw the emergence of new technologies that drove wealth creation. Currently, interest rates are at historic lows, making equities relatively more appealing. The author argues that distinguishing periods when fundamental factors are truly different is important for investment decisions. Sometimes markets reflect collective madness, while other times data shows a real change. Investors need to recognize differences in economic environments.