CHICAGO -- Irascible investing legend John Bogle questioned whether target-date mutual funds are the right retirement investment choice in all cases.

The Vanguard founder told a crowd at the 25th annual Morningstar Investment Conference that anyone who will be receiving Social Security payments already has a large portion of their “retirement assets in as secure an investment as anything can be in this market.”

“The thinking with target-date funds is ‘don’t put yourself into a position of having to make judgments, because they are so often wrong,’” Bogle said, “but I think target-date funds have too narrow a mandate. You have to think about your entire target-date environment.” For example, he said, if your expected lifetime payout from Social Security is $350,000 and you have $350,000 in a 401(k) invested entirely in equities, “you’re not 100% in equities, you actually have a 50/50 split,” he said.

Bogle’s contrarian perspective casts doubt on a retirement product employed by a significant portion of the investing public. Target-date funds have grown in popularity, especially among younger investors, and these funds now hold 13% of total 401(k) assets, according to a recent analysis by the Employee Benefit Research Institute and the Investment Company Institute.

Bogle’s comments touched on a recurring theme that has emerged at this year’s conference – an investor’s entire financial picture, not just investments, should be considered when structuring a portfolio and retirement plan.

Although the retirement system is “a train wreck,” said Bogle, investors can do much to help themselves by focusing on their retirement income stream and not on the fluctuations of the stock market.

“We’re all transfixed by the movement of the stock market,” he said. “But it has absolutely nothing to do with retirement. What you should be looking at is your stream of income.”

This, Bogle conceded, “would suggest more focus on dividend stocks and not growth stocks, and this is a fad these days and maybe dividend stocks are overpriced as a result.” But he encourages investors to keep in mind that the goal of retirement investing is the ability to “go to the mail box and pull out two envelopes, one from Social Security and one from your retirement account. That’s what should matter to you in retirement.”