HYG is an ETF designed to track the Markit iBoxx USD Liquid High Yield Index, which is made up of U.S. dollar-denominated, below-investment-grade ("high yield") corporate bonds with a rules-based, liquid-bond selection approach. In practice, its day-to-day moves are dominated by two variables: changes in Treasury yields (rates) and changes in credit spreads (the extra yield investors demand for default risk). (ishares.com)

With HYG up ~0.00% today, the setup looks like a typical "carry" session where coupon income and small bond price moves roughly offset each other. The key macro reason this can happen is that both legs of high-yield pricing appear relatively stable: (1) Treasury yields aren’t making a decisive one-day move and (2) high-yield spreads are still near relatively tight levels versus recent months, which reduces the odds of a big price swing without a fresh shock. (fred.stlouisfed.org)

Fed/rates expectations: High yield can be sensitive to any repricing of the Fed path because it affects both the risk-free curve and financial conditions; recent Fed commentary has kept the market alert to the possibility of policy staying restrictive for longer (or even tightening if inflation re-accelerates). Credit-risk pricing: The most direct "health check" for HYG is the level and trend of high-yield option-adjusted spreads; when spreads widen, HYG usually falls even if Treasury yields are steady. Positioning/flows: HYG can also be supported by creation-driven demand when inflows are strong, but flow data tends to explain multi-day pressure/support more than an intraday flat tape. (apnews.com)