The Only Spending Rule You Will Ever Need

From Financial Analysts Journal article by M. Barton Waring and Laurence Siegel.

It may be a slight overstatement but they make the case that the decision rule you want to work with in the decumulation phase if you don't want to run out of the money is as follows:

"Each year, one should spend (at most) the amount that a freshly purchased annuity - with a purchase price equal to the then-current portfolio value and priced at current interest rates and number of years of required cash flows remaining - would pay out in that year." [they call this the annually recalculated virtual annuity or ARVA]

Investors who behave in this way will experience consumption that fluctuates with asset values, but they can never run out of money.