From housing economist Tom Lawler:
Folks who expected that mortgages rates would decline when the Federal Reserve began cutting its federal funds rate target range have been dazed and confused over the last month and a half. Since the day before the Fed’s 50 bp reduction in its funds rate target on September 18, 30-year MBS yields have surged by 84 to 96 bp, while mortgage rates have jumped by 72 to 89 bp. At the same time intermediate- and longer-term Treasury yields have risen 53 to 67 bp.
There are two main reasons MBS and mortgage rates have risen by more than Treasury rates over this period. First, implied interest rate volatility has surged, as many market participants were caught off-guard by the string of unexpectedly strong economic releases (and slightly higher inflation releases) following the Fed’s rate decision. For example, the BofAML MOVE index, a measure if implied interest rate volatility derived from one-month options on Treasuries across the yield curve, increased from 101.58 on September 17 to 130.92 on October 28, its highest reading since October 30, 2023. (Mortgage investors effectively write a prepayment option to home borrowers, and as such higher implied interest rate volatility increases the premium over Treasuries that investors require to compensate them for prepayment risk.)
And second, MBS option-adjusted spreads, which were at the low-end of the “no Fed MBS intervention” range just prior to the Fed’s action, have since moved higher.