The so-called Magnificent Seven stocks have delivered remarkable returns over the past three years, fueled by the promise of AI and the unrivaled ability of U.S. corporations to generate outsized profits.2 Strong performance from the top has also improved the quality attributes of broad indexes, reducing average leverage and increasing profitability metrics.3 In a world of structurally higher interest rates, this continues to underpin our preference for high quality, primarily large cap, U.S. companies.
The flip side to this remarkable performance, however, is a historic rise in concentration: market cap-weighted indices like the S&P 500 are as concentrated as they have ever been. Thirty years ago, the top 20 names in the S&P 500 represented about 28% of the total index. Today, the top 20 names account for over 40%.4
The same phenomenon is happening at a global level as well, where the share of U.S. equities in global indexes has also reached record highs. In 2005, the U.S. made up just 50% of the MSCI All Country World Index (ACWI) universe (Figure 3). Twenty years of American exceptionalism later, that number has climbed to 64% (Figure 3).
While an overweight position in U.S. large caps has paid off over the last decade and a half, concentration risk is still a top cited concern amongst investors we speak to. As leadership narrows, headline-level returns are increasingly beholden to a smaller list of constituents and countries, potentially making portfolios riskier overall.
Alongside the tailwind of a declining dollar, we favor international indexes as a diversification tool precisely because they have bucked the concentration trend. Since 2005, the three largest countries in MSCI ACWI ex-USA Index â the U.K., Japan and France â have steadily ceded ground, with their combined weight declining as leadership has broadened out.5