Week 9 Day 3: Cash Is Melting

People think cash is safe. Technically, the dollar amount does not decrease. But the purchasing power does. At 3% inflation and 1% interest, you lose 2% of buying power every year. Over 20 years, that is 33% of your purchasing power gone. Cash feels safe. Inflation makes it the opposite.

This is the paradox of safety: the thing that feels safest (cash) is actually losing value, while the thing that feels dangerous (stocks) is actually growing value over time. Since 1926, the S&P 500 has returned roughly 10% nominal (7% real), bonds have returned roughly 5% nominal (2% real), and cash has returned roughly 3% nominal (0% real). Cash -- after inflation -- has been a zero-return asset for nearly a century. Every year you hold excess cash beyond your emergency fund, you are choosing a guaranteed loss of purchasing power over a historically positive expected return. This does not mean you should invest your emergency fund or next month's rent. Short-term money needs to be in cash. But any money you will not need for 5+ years is deteriorating in a savings account. The 'risk' of investing is volatility (temporary ups and downs). The 'risk' of not investing is permanent loss of purchasing power.

Zvi Bodie and others have argued that the risk-free rate is more properly considered the real (inflation-adjusted) return on Treasury Inflation-Protected Securities (TIPS), not the nominal return on cash or treasuries. By this measure, the 'risk-free' real return has been approximately 0-2% historically. Holding cash at rates below inflation means accepting a guaranteed negative real return -- which is mathematically worse than a 50/50 gamble that has an expected positive real return. The equity risk premium (the expected excess return of stocks over risk-free assets) is estimated at 3.5-5.5% depending on the measurement period and methodology. This premium exists precisely because stocks are volatile -- it is the compensation for enduring volatility. Refusing to invest in equities means declining this premium and accepting the guaranteed real-return erosion of cash. Over 30 years, the cumulative cost of this refusal at a 4% equity risk premium is approximately 3.2x your starting capital.