Starting in 2021, BRK.A's volume surged due to FINRA rules and fractional share trading, creating phantom volume, distorting BRK.B’s relationship, and limiting arbitrage. A 2024 rule change reduced this, highlighting the need for market transparency.
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Abstract
Starting in February 2021, surging Berkshire Hathaway-A volume mystified market watchers. Averaging 375 shares for a decade, daily volume rose to over 20,000 shares, then plummeted nine-fold in June 2024. We demonstrate that the increased volume was nonexistent — the result of reporting rules, retail trading, and fractional shares. Phantom volume created dislocations in BRK.A's relationship to BRK.B, missed arbitrage opportunities, higher trading costs, and incentivized manipulation. Its subsequent reduction was also due to regulatory change. We argue that shortsighted regulations impose a new “limit to arbitrage”, and improving transparency in the national market system is the real mystery to solve.