May 2026 in returns

May belonged to the machines — specifically, the ones that build AI. It was a melt-up in data-center and memory names that beggared belief: Dell more than doubled (+101%), Micron gained 88%, and Snowflake and Datadog rose 87% apiece, with Astera Labs (+76%) and Supermicro (+68%) close behind. The AI-capex trade was at peak enthusiasm, and the indices rode it — the Nasdaq climbed 8.4%, the S&P 500 5.2%, and Japan's Nikkei 11.9% — even as breadth stayed merely decent (53% of stocks green), a hint that a handful of giants were doing much of the heavy lifting.

Almost everything else took a back seat. Crypto sat the rally out entirely — Bitcoin slipped 3.5% and Ethereum 11.1% — and the month's losers were a roll-call of the unglamorous: Ubiquiti (-42%), Zoetis (-32%), AutoZone (-21%), and the whole energy complex, with crude and gasoline futures each down 17-19%. With the benefit of what came next, May reads as the crest: several of the very names that went vertical here — Astera Labs and Rocket Lab among them — would turn up on July's list of steepest decliners. Enthusiasm this concentrated is rarely the kind that lasts.