A Share Trading Volume


Robinhood! Deliciously ironic.

A sudden surge in trading volumes in class A shares of Warren Buffett’s Berkshire Hathaway Inc. BRK.B 2.64%? confounded investors last year. Now, a trio of academics say they have solved the stock-market mystery.

The jump in volumes was an illusion caused by a change in how Robinhood Markets Inc. HOOD 4.76%? reports fractional trades, according to a new study expected to be released Wednesday.