For decades, a divide has limited the options for American workers who are saving for retirement. Assets held outside of retirement plans have access to hedge funds, private equity, real estate partnerships, and other alternatives that move differently from the stock market and can offer different kinds of returns. Meanwhile, 401(k) plans have long offered a limited menu — stock funds, bond funds, a target-date fund, perhaps a money market option, and little else. A new Trump administration policy may close this gap.