Nasdaq 100 index to undergo special rejiggering because a few tech stocks have gotten too big

The rapid rise of a few already-massive tech stocks this year is causing Nasdaq to make unusual adjustments to its popular growth index.

The company announced July 7 that it will do a special rebalance of the Nasdaq 100 Index, which will take effect before the market opens July 24.

The Nasdaq 100 index comprises 100 of the largest nonfinancial companies that trade on the exchange and is often seen as a proxy for growth stocks. The index has surged about 37% year to date, well above the S&P 500 and the Dow Jones Industrial Average.

Nasdaq said a special rebalance can be used to “address overconcentration in the index by redistributing the weights.”

While the index is already rebalanced on a quarterly basis, Nasdaq tries to keep the five biggest stocks below a 40% combined weighting in one rebalance per year designated as the annual adjustment, according to the firm’s methodology. The five biggest stocks appear to be over that threshold currently, according to the holdings of the Invesco QQQ ETF, which tracks the index.

The QQQ’s holdings show how concentrated the index has become. The three largest positions — Microsoft, Apple and Nvidia — account for more than 30% of the fund combined, as Nvidia’s stock price has nearly tripled this year. The top 10 holdings account for a combined weighting of nearly 59%.

This is the third special rebalance on record for the Nasdaq 100. The company said it will announce new weightings July 14.

“The special rebalance is part of the Nasdaq-100 methodology and ensures that index-tracking funds maintain compliance with fund diversification rules. Nasdaq-100 special rebalances have taken place previously in 2011 and 1998,” Cameron Lilja, global head of index product and operations at Nasdaq, said in a statement.

There are several index funds that track the Nasdaq 100, including the QQQ, which has about $200 billion in assets under management.