The single number that predicts a household's financial trajectory better than income, investment return, or spending discipline is the savings rate — savings divided by after-tax income. It is the master variable, and it is fully within the household's control.
- 01Compute a household savings rate honestly.
- 02Explain why savings rate dominates investment return over most working lifetimes.
- 03Set a savings-rate target and a plan to reach it.
The math
Savings divided by after-tax income. Savings includes retirement contributions, above-minimum debt paydown, and cash accumulation. It excludes appreciation on assets you already own — that is investment return, a different variable.
Why it dominates
Over a thirty-year working life, doubling the savings rate from 10% to 20% has a larger effect on ending wealth than raising the investment return by two percentage points. The savings rate is compounded by every year it persists; the investment return is compounded by the base to which it is applied.
The target
Twenty percent is a defensible starting target for a household in early career. Higher is achievable in the years before children and after they leave. Households with above-median incomes should target thirty and above; the lifestyle drag is smaller than they fear.
- Savings rate is the master variable.
- Compounding a higher savings rate beats compounding a higher return.
- Twenty percent is the floor. Thirty is the target for those who can.