Market Broadening, AI, and the Case for Diversification

The investment professionals at Northwestern Mutual Wealth Management Company (NMWMC) provide views and commentary on the current marketplace. This content is intended to communicate our current views on the relative attractiveness of various asset classes and asset allocation strategies over the next 12 to 18 months.

Keep in mind that this viewpoint can and will change as valuations and economic variables evolve. These views should be considered in the context of a well-diversified portfolio, not in isolation, and do not offer recommendations for individual investors. Investment decisions should always be made on an individual basis or in consultation with a financial advisor based on an individual’s preferred risk levels and long-term goals.

 

Section 01: A tale of three markets

The first half of 2026 can be defined as a tale of three markets, with the opening two months of the year seeing a continuation of a broadening trend that began in the back half of 2025 after the Federal Reserve began reducing short-term interest rates toward a cumulative 0.75 percent of monetary easing by year-end 2025. With investors pricing an additional 50–75 basis points (bps) of cuts by the end of 2026, interest rates across the Treasury yield curve pushed sharply lower, with both the two- and the 10-year Treasury falling to 3.37 percent and 3.94 percent by February 27, 2026.

Throw in a healthy dosage of impending fiscal stimulus from the impacts of the One Big Beautiful Bill Act that was expected to increase economic growth, and the market began the year broadening ahead of what investors expected to be a wider economic expansion.

The bifurcated economy that we’ve consistently pointed to over the past few years—which has driven a similarly bifurcated market—finally appeared poised to narrow, as its primary driver, higher interest rates, began to ease.

As expected, this positively impacted our portfolios, which remain positioned for an economic and market broadening—though that outcome may follow a temporary “hiccup” if the Fed is ultimately forced to overtighten policy to bring inflation lower. Interest rate- and economically sensitive U.S. Small- and Mid-Cap stocks each rose nearly 8 percent, outpacing the artificial intelligence (AI)-heavy S&P 500, which rose a mere 0.67 percent as the Magnificent Seven and previously broader technology sectors each fell nearly 6 percent. However, the equal-weight S&P, which removes the concentration bias of AI and technology stocks, rose 7 percent as over 66 percent of the 500 stocks in the roster beat the index. International developed and emerging-market stocks continued their strong 2025 run, rising 10 and 15 percent, respectively. Investors were repositioning for a broader economy and broader earnings growth across corporate America given lower interest rates. That story changed abruptly on February 28, when the Middle East conflict ignited and interest rates began rising once again on the back of the potential for higher energy prices. This led to higher inflation, prompting the Fed to employ a “wait-and-see” approach when it comes to interest rates.

The two-year Treasury rose sharply to a high of 4.12 percent, with the 10-year pushing to a recent high of 4.66 percent. While stocks initially pulled back, they bottomed on March 30 with the announcement of a potential ceasefire. However, equity markets once again narrowed as investors positioned for a probability that higher rates would once again pressure the interest rate-sensitive parts of the U.S. economy. As a result, the markets narrowed to refocus on the AI theme, which has been largely unaffected by the performance of the overall economy over the past few years. From February 28 to June 2, 2026, the S&P 500 climbed 10.9 percent, making U.S. Large-Cap stocks one of the top-performing asset classes. This gain was largely driven by the technology sector, which surged 35 percent. However, performance was much narrower than it appears. The equal-weight S&P 500 rose just 2.9 percent, and only 24 percent of companies outperformed the index. Smaller companies lagged behind Large Caps, with Small-Cap stocks rising 7.7 percent and Mid-Cap stocks gaining 5.4 percent.

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