The average 2015 target-date fund allocated roughly 40% to stocks at the end of 2012, down nine percentage points from the end of 2008, according to Lipper.

WSJ: 'Target' Funds Still Missing the Mark on Returns

For savers still playing catch-up, one strategy is to switch to a target-date fund with a later date and greater exposure to riskier assets that can generate bigger returns.

WSJ: 'Target' Funds Still Missing the Mark on Returns

Investors willing to take additional risk might also consider leaving their current 401(k) savings in a target-date fund, but direct all new contributions into a domestic equity fund or international stock fund to boost returns, says Michael Francis, president of Francis Investment Counsel, a consulting firm specializing in retirement plans.

WSJ: 'Target' Funds Still Missing the Mark on Returns