The S&P 500 didn't gain ground in 2015, so neither did retiree Bruce Stanton's spending money. That summer, the former teacher in Washougal, Wash., dialed back what he withdrew from his retirement account to reflect the lackluster market. Fluctuations in income aren't that rare. During his career as a chemistry teacher, Stanton would sometimes get a big raise and other times get none. "I'm used to going without them," says Stanton, 63.

A challenge for all retirees is creating an income stream that will last a lifetime even if a downturn takes a big bite out of their savings. Some, like Stanton, are tackling this by adjusting withdrawals based on the market's performance.

But market-linked approaches run counter to the long-standing 4% rule, which holds that your money will last for a 30-year retirement if you withdraw 4% of your nest egg the first year and adjust that dollar amount annually for inflation.

Some experts are now arguing for a lower initial rate—such as 3%—since stocks and bonds may deliver below-average returns over the next few decades. Yet for much of history, 4% has been conservative, according to financial adviser Michael Kitces.

So what's a retiree to do? As an alternative to withdrawing a fixed percentage, here's a look at four "dynamic" withdrawal strategies.

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