For armchair investors and retirement savers, "diversification" has come to mean a lot more than buying both stocks and bonds. And a "diversified" portfolio, in the 2020s sense of the term, did really well in 2025. Morningstar estimates that a broadly diversified asset mix, comprising 11 investment classes, gained 18.3% in 2025. That’s a better return than investors would have reaped by investing solely in U.S. stocks, which rose by about 17% on the year. And it’s a much better return than Morningstar ...