This is a metric for tracking a collection of securities. For example, among US stocks, a commonly referenced index is the S&P 500. An index may be price-weighted, market-capitalization weighted or some other way to determine how much of the index each security contributes.

This is a mechanism for tracking a collection of securities. For example, among US stocks, there is the S&P 500 that is a commonly referenced index. An index may be price-weighted, market-capitalization weighted or some other way to determine how much of the index each security contributes.

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