Networking systems provider Ciena Corp is poised to join the S&P 500 index, replacing Dayforce after the software firm was acquired and taken private by investment firm Thoma Bravo for $12.3 billion. The index adjustment, which takes effect before markets open on Monday, triggered a 4% rise in Ciena's shares during after-hours trading. Such shifts often lead to increased demand for the incoming stock as index-tracking funds are forced to adjust their holdings. Thoma Bravo’s move to take Dayforce private highlights a continuing trend of private equity firms targeting established software-as-a-service companies. Simultaneously, Arrowhead Pharmaceuticals will move to the S&P Midcap 400 to fill the vacancy left by Ciena, while security firm ADT joins the S&P SmallCap 600, reflecting a broader reshuffling of corporate valuations.
First published Mon, Jul 13, 2026 · Pitre Media Publication · Non-partisan editorial standard →
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