The operator of the Nasdaq stock market said the rebalance will bring the weights of the companies in the index closer in line with their actual market capitalizations.

It will not change the methodology used to calculate the index or the index securities.

Apple currently accounts for 20 percent of the index, and the rebalancing will bring that share down to 12 percent.

In premarket trading, Apple shares are down more than three percent.

The special rebalance will occur before the market opens on May 2.