These retirement saving 'rules' just don't add up

CNBC - For years, financial advisors have tried to keep retirement planning simple. You can count on the stock market returning roughly 7 percent a year over the long run, according to the conventional wisdom, and expect to withdraw about 4 percent from your nest egg every year once you're retired.

A 2013 study by Michael Finke at Texas Tech and co-authors, for example, plotted the "failure rate" (meaning you'll run out of money) of a retirement account over 30 years, using various annual rates of withdrawal.

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