As the pandemic consumes the nation, millions of housebound Americans have immersed themselves in a new hobby: trading stocks. Lured by the ability to make commission-free trades, online brokerages—like Charles Schwab, Fidelity, and TD Ameritrade—have seen an uptick in users this year. One popular trading app, Robinhood, has reached a staggering 13 million customers. The company raked in $180 mil