Today we’re going to look at the NASDAQ 100, an index designed to track the 100 largest non-financial companies on the Nasdaq:

 Current Weightings in the Nasdaq 100*: 

  1. Apple:                   20.2%
  2. Microsoft:           4.3%
  3. Google:                4.2% 

Actual Weightings based on true Market-Cap**: 

  1. Apple:                   10.9%
  2. Microsoft:           10.6%
  3. Cisco:                    6.2% 

The difference is due to adjustments made to the index in 1998 to lower the weighting of Microsoft at that time.

 *as of 6/28/2010

**as of 5/30/2010

 Source:  Bloomberg, Nasdaq, San Francisco Chronicle