Hunch. Berkshire has already trailed the index by about nine points this year, so it enters this window behind rather than level, which is where most of the thirteen started.
This market compares two percentage changes from 18 September 2026 to 18 December 2026: Berkshire class B from its close of $509.77, read on the Nasdaq price page for BRK/B, and the S&P 500 index from its close of 7,650.50, read on the S&P Dow Jones Indices page. YES if the Berkshire change is the smaller of the two, NO if it is equal or larger; if either source is unavailable the closing levels reported by two of Reuters, the BBC and the Financial Times settle it.
We looked for S&P 100 companies where a founder, or someone who had chaired the board for ten years or more, gave up the chair while another person was already chief executive. We found thirteen cases since 2010 and show them all. For each, we checked whether the shares closed below the announcement-day price four weeks later. In eleven of the thirteen the shares dipped below that price within five days, so the first days say little. At Microsoft and Oracle, both in 2014, a new chief executive was named on the same day, so those price moves were not about the chair alone.