Robinhood's outsized percentage increase accounts for the fact that it was much smaller to start, Rowady said. Robinhood makes money by taking a fraction of a cent per dollar from each trade order and collecting interest on customers' deposits. It also has a paid subscription service called "Robinhood Gold," unveiled in September 2016. As a private company, Robinhood is not required to disclose its income statements, which would paint a better picture of its revenue components. As a registered broker-dealer, though, it does have certain required disclosures, which Alphacution used to estimate its totals.