Indexes can be built in a number of ways, often with consideration to how to weight the various components of the index. The three main ways include: A market-cap, or capitalization-weighted index puts more weight in the index to those components that have the largest market capitalization (market value), such as the S&P 500 A price-weighted index puts more weight to those components with the highest prices (such as the Dow Jones Industrial Average) An equal-weighted index allocates each component with the same weights (this is sometimes called an unweighted index)