{"updated": "2026-07-11", "source": {"name": "S&P 500 constituent weights + Yahoo Finance (IWB/IWM, top-3 stocks)", "method": "Replication of Mauboussin & Callahan, 'Stock Market Concentration' (June 2024), exhibits 1/8/11. Live top-N weights are shares of S&P 500 total cap (the paper uses share of ALL listed U.S. stocks, a broader denominator, so paper levels run lower). Share classes merged per company. IWB/IWM dividend-adjusted closes proxy Russell 1000/2000 total returns."}, "topShares": {"asOf": "2026-05-13", "top1": 6.09, "top3": 17.69, "top10": 36.11, "top10Names": ["AAPL", "MSFT", "NVDA", "AMZN", "GOOGL", "META", "BRK.B", "TSLA", "AVGO", "WMT"]}, "paperExtension": {"asOf": "2026-07-10", "points": [{"year": 2024, "ytd": false, "top1": 5.5, "top3": 15.4, "top10": 30.4}, {"year": 2025, "ytd": false, "top1": 5.8, "top3": 16.7, "top10": 33.3}, {"year": 2026, "ytd": true, "top1": 4.7, "top3": 16.5, "top10": 33.6}], "method": "S&P 500 caps approximated from current weights x price ratios, rescaled to the paper's end-2023 all-US levels."}, "sizeSeries": {"months": ["2000-05", "2000-06", "2000-07", "2000-08", "2000-09", "2000-10", "2000-11", "2000-12", "2001-01", "2001-02", "2001-03", "2001-04", "2001-05", "2001-06", "2001-07", "2001-08", "2001-09", "2001-10", "2001-11", "2001-12", "2002-01", "2002-02", "2002-03", "2002-04", "2002-05", "2002-06", "2002-07", "2002-08", "2002-09", 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