The Materials Select Sector SPDR ETF (XLB) experienced a significant downturn of -2.52% during the regular market session on July 31, 2026, a move that went against the generally positive trend in the broader market, which was buoyed by strong tech earnings. There was no single, clear catalyst identified in market news or commentary to explain this specific and substantial drop in the materials sector. Earlier in the week, earnings reports from major materials companies were mixed, which may have contributed to underlying investor caution within the sector.