Nasdaq OMX has announced a rare rebalancing of its Nasdaq-100 index, which will reduce the “big weighting” of Apple, reports the “Wall Street Journal” (http://online.wsj.com/article/SB10001424052748704587004576243231566493842.html). The company currently makes up more than 20% of the index.

Apple’s stock value accounts for just over 20% of the index, but after the restructuring it will account for slightly over 12%. Still, at 12.3% Apple will still be the largest single component on the index.

The rebalancing was driven in part by “the seemingly unstoppable rise in Apple shares, which are up more than fourfold in the past two years,” says the “WSJ.”