Target-date fees, returns

Among the top 20 target-date funds by assets, Vanguard not only posts the lowest average expense ratio, but also the best risk-adjusted returns. Vanguard's average three-year Sharpe ratio was 1.01, followed by Fidelity, at 0.95, and T. Rowe Price, with 0.94. Average five-year Sharpe ratios were: Vanguard, 0.12; T. Rowe Price, 0.11; and Fidelity, 0.07.

The weighted average expense ratio for target-date fund series with at least $5 billion in assets was 0.59% as of Dec. 31. Excluding Vanguard, the average was 0.77%, and expanding the universe to include all target-date series, the average climbed to 0.99%.