The Nasdaq 100 will complete an out-of-cycle 'special rebalance' over the weekend, designed to reduce the weightings of the largest names in the index.
Apple, Microsoft, Alphabet, Amazon, Meta Platforms, NVIDIA and Tesla have risen by around an average 60% in the year to date – including the best first half for 40 years – and now make up 55% of the index.
Microsoft's weighting will fall from its current 12.74% of the index to 9.80%; Nvidia from 7.28% to 4.30%; and so on.
A special rebalance "may be conducted to address overconcentration in the index by redistributing the weights" but "will not result in the removal or addition of any securities", Nasdaq said in a statement earlier this month.
Changes will be effective from 24 July.
"In all, it will mean these six stocks don’t make up more than 40% of the NDX," said market analyst Neil Wilson at Finalto.
"I don’t think it amounts to a hill of beans – the Nasdaq 100 is already a kind of weird tech bubble measure. But a case in point – NDX equal weight declined by around half the amount the market cap weighted index did yesterday."