U.S. stock futures were dropping in thin trading on Monday, as lingering concerns about elevated interest rates and the government’s mounting debt burden spoiled any chance of an end-of-year party for markets. Investors are still fretting that the Federal Reserve won’t cut interest rates by as much as they were hoping in 2025, with inflation still running clear of the central bank’s 2% target. Treasury Secretary Janet Yellen also gave markets a sobering reminder about the deficit on Friday.