What are the key differences between the S&P 500 and the Dow Jones Industrial Average (DJIA) in terms of company representation and Index calculations? The S&P 500 represents a much fewer number of companies and is weighted based on company stock prices, while the DJIA represents a much larger number of companies and its index is market cap weighted. The S&P 500 represents a much larger number of companies and is weighted based on company stock prices, while the DJIA represents much fewer companies and its index is market cap weighted. The S&P 500 represents a much larger number of companies and is market cap weighted, while the DJIA represents much fewer companies and its index is weighted based on company stock prices