Interesting chart! While this does show the potentially drastic impact that one company can have in a 30-constituent index, the S&P 500 (with its market-cap weighting) is not completely immune from one company potentially dominating as well.
For example, IVV, an index ETF that tracks the S&P 500, currently has > 4% of its assets in AAPL[0], due to Apple's immense market cap.
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Interesting chart! While this does show the potentially drastic impact that one company can have in a 30-constituent index, the S&P 500 (with its market-cap weighting) is not completely immune from one company potentially dominating as well.
For example, IVV, an index ETF that tracks the S&P 500, currently has > 4% of its assets in AAPL[0], due to Apple's immense market cap.
0. http://www.ishares.com/us/products/239726/ishares-core-sp-50...