Nasdaq has announced that SpaceX (SPCX) will be added to the Nasdaq-100 Index® (NDX®) starting Tuesday July 7, 2026. This addition, like many over the past few years, has been telegraphed by Nasdaq through a recent announcement. Although the SPCX addition is a bit higher profile than other stock added to NDX, there is a historical pattern that traders should be aware of going into this index addition.
We did a little digging into NDX additions going back to the beginning of 2022. There have been forty-two NDX additions since the start of 2022. Of those, seven were spinoffs or done on short notice. The remaining thirty-five, that are used to analyze the price behavior of additions, were announced at least ten days before being added to the index. We stick with those thirty-five stocks as the other seven did not have the same notice as SPCX or many recent additions.
Our first look is at the one-day stock performance on the day the stock is added to the index. Index funds will buy shares on the close the day before the stock is added on the following trading day on the open. The result is often weakness for a stock the day it is added to NDX. The chart below shows the first day performance for the thirty-five appropriate additions to the index since 2022 in order of addition.
Source: Bloomberg, Author Calculations
The chart showing first trading day’s performance was a lot redder than green, as most stocks added to the NDX trade lower on their first day. Specifically, of the thirty-five additions, only twelve rose on the first day as a member of NDX. The average change is a loss of 1.13%. The best performing stock is one of the most recent additions in Teradyne (TER), which gained 4.36% and worst was MicroStrategy (MSTR) with a loss of 8.78%.
A second run looked at the first five-day performance for new NDX stocks, and the results were very similar. The average change for a stock added to the NDX is a loss of 3.41% over the first five days. The range of gains and losses is massive, with AppLovin (APP) putting up a gain of 14.50% and the worst performer being Rocket Lab (RKLB), which was 21.17% lower in the first five days as an NDX member. Finally, the win rate was lower with only eleven stocks gaining value in the first five days in the NDX.
Source: Bloomberg, Author Calculations
The data paints a consistent picture that joining NDX has historically been more of a “sell the news” event than a catalyst for gains. With only twelve of thirty-five additions posting a positive first day, and just eleven managing to close higher after five days, the odds have favored short-term weakness rather than strength — averaging losses of 1.13% and 3.41%, respectively. The forced buying from index funds ahead of inclusion appears to pull demand forward, often leaving little fuel left once the stock joins.
For SpaceX, the situation carries an extra layer of uncertainty given its high profile and the intense investor interest surrounding the company. That popularity could work in either direction — it might mean an outsized amount of index-related buying has already been priced before July 7, setting up the kind of post-inclusion fade seen in names like MicroStrategy and Rocket Lab. Or, given the level of enthusiasm around the stock, SPCX could defy the historical trend the way Teradyne and AppLovin did.
What history suggests is that traders shouldn’t assume inclusion in the NDX is automatically bullish. The pattern of weakness in the days following addition has been persistent enough over the past several years that it’s worth factoring into any short-term positioning around SPCX’s debut in the index.
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