Bond yields just hit 3-year highs, pushing mortgage rates up and threatening housing affordability. Ben Casselman, chief economics correspondent for The New York Times, explains why Treasury yields are rising, whether it signals economic strength or fiscal danger, and what it means for your wallet. The U.S. Treasury market, a $30 trillion system, sets interest rates for mortgages, auto loans, and business borrowing, making bond yields the most important financial benchmark on Earth.