U.S. equities opened higher on Wednesday, with the S&P 500 up 0.52% at 6,377.95, the Nasdaq Composite 0.78% firmer at 21,335.12 and the Dow Jones Industrial Average ahead 0.61% at 44,462.28. The advance followed a 0.7% rise in the S&P 500 a day earlier. Behind the headline gains, participation continued to narrow. Fewer than half of S&P 500 constituents are trading above their 50-day moving average and only about 50% remain above the 200-day benchmark. Market data from Aug. 5 showed just 49.7% of listed shares advancing, down sharply from 80.4% the previous week. The equal-weight version of the index was marginally negative and the small-capitalization-heavy Russell 2000 slipped 0.3% on Tuesday, underscoring the loss of breadth. Volatility also retreated. The CBOE Volatility Index hovered near 16.7 after having spiked above 21 late last week. Options desks noted heavy negative gamma exposure around the 16 level, suggesting market makers could damp price swings near that threshold but warning of a potential volatility expansion if support fails. The 10-year Treasury yield was little changed around 4.22%. The combination of headline index strength, thinning breadth and subdued volatility highlights investors’ growing reliance on a shrinking group of large-capitalization stocks as benchmarks hover close to record highs.