Morningstar: 60/40 Model Beats Diversified Portfolios Over the Long Term

Why It Matters

The study signals that over the long run, piling on niche assets can erode portfolio performance, prompting wealth managers to favor leaner, bond‑centric allocations. It also underscores the enduring relevance of the 60/40 framework for risk‑adjusted returns.

Key Takeaways

• 2025 diversified test portfolio returned 18.3%, 0.5% above 60/40
• Over 20 years, 60/40 yielded 9.68% vs diversified 7.13%
• International equities and high‑quality bonds provide strongest long‑term diversification
• Alternative assets like private equity, crypto should stay under 5% allocation
• Asset class correlations rise in market stress, reducing diversification gains

Pulse Analysis

The 60/40 portfolio—half U.S. equities, half investment‑grade bonds—has long been the benchmark for balanced investing. Morningstar’s latest report shows that in a volatile 2025, a more diversified mix that added international stocks, multiple bond categories and small allocations to commodities and REITs nudged total returns to 18.3%, modestly beating the traditional split. This short‑term edge sparked renewed interest in multi‑asset strategies, especially as investors chased higher yields amid lingering post‑pandemic uncertainty.

However, the data reveal a different story when the lens widens. Over ten and twenty years, the plain 60/40 outperformed its diversified counterpart, delivering 9.55% and 9.68% annualized returns versus 8.19% and 7.13% respectively. The advantage stems largely from the stable correlation between U.S. stocks and high‑quality bonds, which historically stays below 0.6. During market shocks—such as the COVID‑19 sell‑off—bonds posted positive returns (2.98% in early 2020, with Treasuries up 15.45%), cushioning equity losses and boosting risk‑adjusted performance.

For practitioners, the takeaway is pragmatic: keep diversification lean and purposeful. Morningstar recommends limiting exposure to alternative assets—private equity, crypto, niche commodities—to under 5% of the portfolio, as their liquidity constraints and volatility can negate diversification benefits when correlations spike. Prioritizing international equities and a core of U.S. Treasury or agency mortgage bonds offers a more reliable hedge against domestic market swings and a potential currency‑depreciation scenario. By aligning allocations with assets that maintain low correlation over time, advisors can preserve the risk‑adjusted upside that the 60/40 model has historically provided.