Market Cap Weighting

Category: finance

An index construction method where stocks are held in proportion to their total market capitalization.

This is the "standard" index. In the S&P 500, a company like Apple (massive) has a much larger impact on the index than a smaller company. It’s why the S&P 500 is so heavily influenced by the performance of the top 10 mega-cap firms.

Common Examples

• The index fund uses market cap weighting, which naturally trends toward the largest and most successful companies in the sector.
• Critics argue that market cap weighting can lead to "momentum chasing," where the fund over-allocates to already expensive giants.