Systematic long-short equity managers, the algorithmic strategies that parse mountains of market data to find statistical edges, just posted their worst multi-day run since 2023.

According to Goldman Sachs prime brokerage data, the first half of January 2026 was the weakest period for systematic long-short equity managers since October 2025, with the cohort losing approximately 1% over a critical 10-day stretch. UBS went further, estimating that US-focused quant funds were down around 2.8% in the first two weeks of 2026 alone.

Who got hit and how hard

Renaissance Technologies saw its strategy down roughly 4% by early January. Schonfeld’s quant operation dropped approximately 3.9% through mid-month. Engineers Gate fell around 6%.

UBS identified one-day deleveraging events as a key driver, describing the unwinding as the sharpest seen since December 22, 2025.

This has happened before, recently

In the summer of 2025, quant equity managers suffered their worst run since the end of 2023, with average losses approximating 4.2%. That episode was driven by momentum unwinds and a sharp rally in lower-quality stocks.

Crowded trades and violent reversals in factor-based positioning were cited repeatedly across the recent reports as the primary mechanics behind the losses.