Compound Growth & The Time Value of Money

Role

Compound interest is simultaneously the most powerful force in personal finance and the most universally underestimated. Einstein is apocryphally credited with calling it the eighth wonder of the world — and whether or not he said it, the sentiment captures a genuine cognitive failure: the human brain is biologically wired to perceive growth linearly and systematically underestimates exponential processes. The practical consequence is that most people start saving and investing later than is optimal — often by decades — producing forgone wealth that no subsequent saving rate can fully recover. A person who invests $5,000 per year from age 22 to 32 (10 years) and then stops will typically have more wealth at 65 than one who invests $5,000 per year from 32 to 65 (33 years). This counterintuitive reality is unknown to the vast majority of people in their twenties, who are at precisely the moment when acting on it would produce the greatest lifetime benefit.