Week 9 Day 7: Invest to Stay Even, Invest More to Get Ahead

Think of the economy as a moving sidewalk. Inflation moves prices forward at 3% per year. If your money grows at 3%, you are standing still -- keeping pace but not gaining ground. At 7%, you are walking forward on the sidewalk -- making real progress. At 0% (cash under the mattress), you are moving backward relative to everything around you.

The 'moving sidewalk' analogy clarifies why investing is not optional -- it is necessary just to maintain your current position. Standing still (cash at 0% real) means falling behind. The minimum acceptable financial outcome is matching inflation. The goal is exceeding it. Here is how common strategies stack up against the moving sidewalk: Cash: moving backward 2-3% per year. High-yield savings: roughly standing still. Bonds: walking slowly forward (1-2% real). S&P 500: walking briskly forward (4-7% real). The difference between standing still and walking forward at 5% real is the difference between $100,000 of perpetual purchasing power and $432,000 of purchasing power in 30 years. Same starting point. Same time. The only variable is where you placed the money.

The concept of the equity risk premium -- the excess return of stocks over risk-free assets -- is the fundamental justification for equity investing. Aswath Damodaran of NYU Stern calculates this premium annually and estimates it at approximately 4.5-5.5% for U.S. equities. This premium has been remarkably stable over the past century despite massive changes in the global economy. The theoretical basis (from the Consumption Capital Asset Pricing Model) suggests the premium compensates for: (1) consumption risk (stocks decline when you most need money -- during recessions), (2) rare disaster risk (small probability of catastrophic loss), and (3) behavioral factors (loss aversion and myopic loss aversion make investors demand higher returns for tolerating volatility). The 'equity premium puzzle' (Mehra and Prescott, 1985) notes that the historical premium seems too large to be explained by rational risk aversion alone -- implying behavioral factors play a significant role. For the individual investor, the implication is clear: the premium exists, it is large, and it rewards those willing to tolerate the volatility that most people cannot stomach.