A surging stock market pushed many retirement account balances to new highs in the waning days of 2023. But for those already spending their retirement nest eggs, these higher balances are a mixed blessing.

The reason has to do with rules that require older people to start taking money out of their traditional pretax 401(k) and individual retirement accounts each year, called required minimum distributions or RMDs. The amount is calculated by taking an individual’s account balance on Dec. 31 and dividing it by their life expectancy.