For the past decade, the spread between a measure of average national mortgage rates and 10-year Treasury yields has averaged 1.8 points, according to figures tracked by Autonomous Research. This year began right around that level. But with Treasurys yielding over 4%, the spread now at roughly 3 points is about as high as it has been this century.

Other times that the spread has seen comparable widening were in late 2008 and March 2020, when the financial crisis and pandemic, respectively, were driving investors to the haven of Treasurys. In both cases, the Federal Reserve stepped up to buy more mortgage bonds, bringing spreads and mortgage rates down, as spreads on mortgage bonds are a key component in the mortgage rates ultimately charged to borrowers.

This time, that isn’t happening.