
S&P rebalancing: Pinterest enters S&P 400; Under Armour drops to small-cap index

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S&P Dow Jones Indices announced index changes effective Dec. 22. Pinterest will join the S&P MidCap 400, while Under Armour will move to the S&P SmallCap 600. Comfort Systems USA will be promoted to the S&P 500. Several companies will be removed from the mid-cap index and others from the small-cap index. Pinterest shares rose nearly 4% premarket.

