Here is one of the biggest retirement mistakes investors make

1:04 PM ET Mon, 16 July 2018

Fund giant Vanguard Group recently reported 51 percent of investors in 401(k) plans with the firm put all their money into a single target-date fund in 2017. Fidelity Investments has similar figures. But some experts warn this hands-off approach can backfire by failing to account for factors like investors’ life expectancy, risk tolerance, income changes or loss of a spouse.