Nasdaq has conducted a special rebalance only twice before -- in December 1998 and May 2011. Nasdaq's rules state that if all stocks with a weighting of more than 4.5% in the index exceed 48%, then Nasdaq rebalances the indicator. Under Nasdaq rules, the rebalancing process sets the aggregate weight of stocks with a weighting of 4.5% or more at 40%.
The special rebalance will be based on index and stock prices as of July 3. Details will be announced on July 14, and will go effective on July 24.