One of These S&P 500 Funds Has Trailed for 10 Years. Its Fans Say That’s the Point.

A ten-year performance comparison between market-cap-weighted and equal-weighted S&P 500 index strategies illustrates the dramatic impact of mega-cap technology concentration on broader market returns. Over the past decade, the market-cap-weighted SPDR Portfolio S&P 500 ETF (SPYM) generated a total return of +322.64%, significantly outpacing the Invesco S&P 500 Equal Weight ETF (RSP), which advanced +202.99%. The outperformance of the market-cap structure is heavily driven by top-heavy exposure to mega-cap technology and platform giants. Major holdings such as Apple (6.59% weighting, totaling $10.1 billion of SPYM's $153.9 billion net assets), Amazon (3.62%), Alphabet, and Broadcom (2.77%) have captured disproportionate market share and momentum. In contrast, equal-weighted strategies distribute holdings evenly across all 500 constituents, leading to heavier tilts in industrials, financials, materials, and real estate. While market-cap indexing continues to lead across shorter and longer timeframes, equal-weight advocates view the structure as critical protection against concentration risk, positioning the strategy to outperform should market leadership rotate away from mega-cap tech.