Both Berkshire Hathaway's Class A and Class B shares reached all-time highs this week. Although weekly gains were modest, their stock prices rose 8.9% overall in October, outperforming the S&P 500's 0.9% decline and the Nasdaq's 5.3% decline over the same period.

Berkshire's stock price surge was driven by a market rotation of funds from overvalued AI and tech stocks towards traditional value stocks. However, one of its significant holdings, Google parent company Alphabet, saw its market capitalization plunge by approximately $500 billion on Thursday, with its stock price falling nearly 13%, marking its largest single-day drop since its 2004 IPO. This was due to Alphabet's third-quarter free cash flow falling significantly below expectations and search revenue missing expectations for the second consecutive quarter, raising investor concerns about the costs of its AI infrastructure development and the impact of AI on its core business. As a result, Berkshire's stake in Alphabet decreased in value from $40 billion in early August to $29.6 billion by Friday, a loss of a quarter of its value.

Additionally, Berkshire sold $69 million worth of DaVita stock this week. This was a routine reduction in accordance with a 2024 agreement, aimed at maintaining its ownership percentage in DaVita.