The Nasdaq 100 Index is a modified capitalization-weighted index designed to track the performance of a market consisting of the 100 largest and actively traded non-financial domestic and international securities listed on the Nasdaq exchange. Also called the NDX, this is one of the few indices in the United States which have foreign companies with stocks issued on the exchange, as constituents.
The NASDAQ 100 index is structured as a hybrid between equal weighting and capitalization weighting. It is similar to a general market cap with one main difference: the largest stocks are capped to a percent of the weight of the total stock index and the excess weight will be redistributed equally amongst the stocks under that cap. Unfortunately, due to changes in stock prices, constant updating for the NASDAQ 100 is required. The market capitalization for each stock used in the calculation of the index is redefined so that each index constituent has an equal weight in the index at each re-balancing date.
Thus, the basic formula used for the index calculations is:
The Adjusting Weight factor of a stock is assigned to the stock at each re-balancing date, which makes the stock value for each stock equal. For index component, the value would be: :
For more information on how stock indices are calculated, go to how stock indices work.
The List of stocks on the NASDAQ 100 as of 22 October 2008