GM's new buyback is worth 30% of the company. The stock had its worst day since July 2025.

General Motors fell 6.84% on 20 October, the day it reported third-quarter results and authorized a $20 billion share buyback. At the close the whole company was worth $67.6 billion on our S&P 500 map, so the new authorization equals about 30% of its market value. It was GM's worst day since 22 July 2025 and the worst move in the S&P 500 that session, on a day when 402 of the index's 500 stocks rose.

What the stock reacted to

The quarter itself beat. $GM reported adjusted earnings of $3.70 a share against $3.63 expected, on revenue of $50.0 billion. Its full-year adjusted EPS range of $12.75 to $13.75 has a midpoint below the $13.41 analysts expected, and the company pointed to about $2 billion of cost headwinds this year from commodities, logistics and memory chips.

GM lost $5.0 billion of market value on the day, a quarter of the buyback it had just announced. $F, the closest comparison on the map, slipped 0.25%.

The buyback GM already ran

This is not GM's first large program this year. The release says it completed a $6.0 billion buyback announced in January, and its share count fell from 904 million at the end of 2025 to 849 million on 30 September, a 6% cut in nine months. The stock closed 2025 at $81.32. Tuesday's close of $77.09 leaves it 5.2% lower for the year.

The new authorization has no expiration date, so the release does not say how quickly the $20 billion will be spent.