The creator of the 4% rule for retirement withdrawals says the next five years could determine whether his rule will remain valid. Bill Bengen, a financial planner in Southern California, published a study in 1994 that said savings could last 30 years if retirees withdrew 4% of their nest egg in the first year, and increased the dollar amount by the inflation rate each year after – assuming the portfolio was held in a tax-deferred account and evenly split between large-company stocks and U.S. Treasury bonds. But two major stock market downturns since 2000 have some observers wondering if Mr. Bengen’s rule still holds. For his part, Mr. Bengen says retirees could have a problem if stock returns stay low with high inflation rates. He doesn’t see a sharply higher interest rate in the near future, “but you never know,” he says.