A drop in mortgage rates spurred a 25.6% month-over-month surge in rate-and-term refinance lock volume in May, according to the latest Market Advantage report from Optimal Blue.

As tracked by the company’s Optimal Blue Mortgage Market Indices (OBMMI), 30-year conforming rates ended May at 7.02%, 22 basis points lower than at the end of April. This is confirmed by similar rate data from Freddie Mac: Average 30-year fixed mortgage rates were at 7.22% during the week ending May 2 and at 7.03% during the week ending May 30.

“The sharp increase in demand for rate-and-term refinances following a dip in rates indicates that homeowners with rates above 7% feel pinched and are sensitive to even modest interest rate movements in the current economic landscape,” said Brennan O’Connell, director of data solutions at Optimal Blue. “For context, since Optimal Blue began tracking the 30-year conforming rate as a market index in January 2017, interest rates only exceeded 7.02% on 120 market days. Based on other measures, buyers who locked loans on those days have the highest mortgage rates of the past two decades.”

The significant monthly spike in rate-and-term refis helped overall mortgage rate lock volume rise by 5.3% in May. Lock volumes in other loan categories jumped as well, up 4.1% in purchase and 7.2% in cash-out refinances. Year over year, overall lock volume is up by 1.8%.

Lock counts, on the other hand, remain soft, with May’s locks down 4% annually. Lock counts and lock volumes can diverge because of the impact of home price appreciation and refinance volatility; despite the disparity, May’s decrease in locks was still stronger than the 7% year-over-year fall posted in February. (February was the last month unaffected by the timing of the Easter holiday. Lock counts rose year over year in April, although the month’s numbers were boosted because Easter fell in March this year. March’s lock count, conversely, was down 24% yearly.)