Most fixed-rate mortgages are packaged into mortgage-backed securities (MBS)—often agency MBS for conventional and government loans. Investors buy these bonds for yield; prices move inversely to yields. When MBS prices fall, mortgage rates tend to rise, and vice versa. That is why rate sheets can change intraday even without a Fed meeting.
MBS do not move in a vacuum. Treasury yields, inflation data, and risk sentiment all spill over. A rally in Treasuries often helps MBS; a selloff in bonds often pressures rates higher. Loan officers do not need to trade bonds—but they should know that "rates went up today" usually means "bond markets sold off," not that a lender randomly changed its mind.
For Realtors, the practical lesson is timing: clients floating their rate are exposed to market volatility. Educate buyers on lock options, float-down policies, and why pre-approval letters should include realistic payment ranges when markets are volatile.
Simple client script: "Mortgage rates follow the bond market. When investors demand higher returns on bonds, home loan rates often move up. We watch that daily so we can lock at the right time." That builds credibility without overpromising a bottom.