FYI: If it feels like diversifying beyond a simple moderate portfolio that owns one U.S. stock index fund and one U.S. bond index fund has been a fool's errand over the past decade, there's good reason for that. Vanguard Balanced Index (VBIAX) had its best decade of risk-adjusted returns since it launched in 1992, and it invests in just two broad U.S. index funds. To be fair, seven of the 153 funds in the allocation--50% to 70% equity Morningstar Category had as good or slightly better risk-adjusted returns over the decade, so there was some room for improvement, but it has still been a fantastic time for simplicity.
Vanguard Balanced Index is a moderate-allocation fund that earns a Morningstar Analyst Rating of Gold. It uses 60% of its assets to track the same index that underlies Gold-rated Vanguard Total Stock Market Index (VTSAX) and 40% of its assets to track the same index underlying Silver-rated Vanguard Total Bond Market Index (VBTLX).
Regards,
Ted
https://www.morningstar.com/articles/931507/vanguards-twofund-portfolio-just-had-its-best-deca.html