UnitedHealth has by far the biggest weighting in the Dow Jones Industrial Average . The 126-year-old blue-chip benchmark is price-weighted, meaning stocks with higher share prices are given the most weight. The health-care stock closed Wednesday at $520.97, while the stock with the second-highest impact on the 30-stock Dow, Goldman Sachs , stood at $327.37, nearly $200 less than UnitedHealth. While almost all other equity indexes are weighted by market capitalization, including the S & P 500 and the Nasdaq Composite , that doesn't mean UnitedHealth's power is diminished. The insurer is so large, with a $486 billion market cap, it ranks as the ninth-biggest company in the S & P 500.

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