Fractional trading brokerages like Robinhood, meanwhile, are “a fly in the ointment,” to Buffett, says Professor Robert Bartlett, who co-authored a new study finding volumes of the most expensive stock in the U.S. have been artificially inflated by the way brokers like Robinhood report fractional trading. “Buffett wants to keep the price of his Class A shares high to attract long-term value investors. Those aren’t the people buying these fractional shares, and so they are undermining his main vision for the stock.”