'The only way to get closer to meeting your spending goals is through some sort of partial annuitization strategy,' said Michael Finke, dean of The American College of Financial Services, at the Retirement Industry Conference in Orlando last week.

Vanguard’s domination of TDF flows in recent years has paralleled its domination of overall mutual funds flows. Competitors search for ways to be different, but not too different.

'This works really well with couples, where the husband is a risk taker but the wife is worried that she’ll be left without any money,' said Curtis Cloke about Retirement NextGen, a new software tool that replicates his planning techniques.

In his latest book, 'Finance for Normal People: How Investors and Markets Behave,' Prof. Statman describes the behavioral-wants frontier. He contends that people seek 'utilitarian, expressive and emotional' benefits from what they buy.