"With 10 years of history, there's now enough of a track record to judge just how well investors are doing in target-date funds. The average per-year return over the past decade was 5 percent ... Stock funds were up an annual 7.5 percent over the past decade, while bond funds were up an average 4.4 percent.... But target-date funds have one big advantage over other kinds of mutual funds ... The average mutual fund has a flaw, which is that the average investor ... tend[s] to jump in and out of funds at the wrong time.... Investors in target-date funds, at least so far, seem to have avoided this curse."