Life Expectancy
Also called: expected lifespan, period life expectancy
Life expectancy is the average remaining years of life at a given age — and planning to it means roughly half of people run out of money. Two subtleties matter: expectancy rises as you age, since you've already survived the risks that killed others, and a couple's joint expectancy is materially longer than either individual's. Retirement plans should target a high percentile, not the average.