Robinhood Traders Playing S&P Index-Guessing Game Get Schooled

In the end, Robinhood Markets Inc. found itself caught in the same kind of trade its users favor: One driven more by speculation than certainty.

Last week, traders were speculating Robinhood would be added to the S&P 500 as part of the index’s quarterly rebalancing. Shares of the online brokerage climbed every day in anticipation, setting four consecutive all-time highs and gaining 13% across five sessions.