Palantir Technologies Inc. shares slumped as much as 11% late Friday amid the annual reconstitution of the Russell equity benchmarks, a reshuffle that forces index-tracking funds to add and drop holdings in one concentrated burst of trading. Market participants cited a block sale of roughly 40 million Palantir shares near the closing auction as a key driver of the sell-off. The Russell 2000 and Russell 3000 rebalance is one of the busiest liquidity events on the U.S. calendar. Goldman Sachs told clients that close-auction volumes for stocks affected by the reshuffle typically swell to between two and three times normal levels, intensifying price swings in the final minutes of the session. While Palantir bore the brunt of selling pressure, megacap technology names including Alphabet and Amazon moved higher into the bell, underscoring how the index changes can send individual stocks in sharply different directions. Traders also reported unusually heavy flows in exchange-traded funds linked to a range of Russell style and size indices.