Under the Employee Retirement Income Security Act, or ERISA, employers and other plan fiduciaries must act prudently and put participants' interests first when selecting and monitoring investments. Employers select the financial providers, target-date funds, mutual funds, and other choices available in a 401(k), but participants typically bear the investment costs and losses. ERISA's fiduciary rules provide an important check by requiring plan managers to carefully investigate and monitor investments and act for workers' benefit.