The Federal Reserve cut interest rates this week, but mortgage rates had their biggest one-week upturn in nearly a year.

According to data released Thursday by Freddie Mac, the 30-year fixed-rate average shot up to 3.73 percent with an average 0.5 point. (Points are fees paid to a lender equal to 1 percent of the loan amount and are in addition to the interest rate.) It returned to levels not seen since early August.

The 17-basis-point spike was the largest one-week increase since October 2018. (A basis point is 0.01 percentage point.) The 30-year fixed-rate average was 3.56 percent a week ago and 4.65 percent a year ago.

The 15-year fixed-rate average climbed to 3.21 percent with an average 0.5 point. It was 3.09 percent a week ago and 4.11 percent a year ago. The five-year adjustable-rate average jumped to 3.49 percent with an average 0.4 point. It was 3.36 percent a week ago and 3.92 percent a year ago.

“Mortgage rates are now noticeably higher than lows reached just two weeks ago, and it appears, at least for now, that the period of historically low mortgage rates may well be a thing of the past,” said Matthew Speakman, a Zillow economist.

The Federal Reserve lowered its benchmark rate this week, its second cut in three months. However, the quarter-point reduction came too late in the week to be factored into Freddie Mac’s survey. The federally chartered mortgage investor aggregates rates from 125 lenders nationwide early in the week to come up with national average mortgage rates.

The central bank’s rate cut is unlikely to have a major effect on mortgage rates. The Fed doesn’t set home-loan rates, but its decisions influence them.

“This rate cut [by the Federal Reserve] does not really affect long-term rates like mortgages,” said Michael Becker, branch manager of Sierra Pacific Mortgage in White Marsh, Md. “However, their take on the economy and the potential for future rate cuts can have an effect on long-term rates like mortgages. Since their statement conveys their expectations for moderate economic growth in the near term and limited need for future rate cuts, I don’t expect them to help long-term rates like mortgages much.”

Instead, a sell-off in the bond market had a more direct effect on mortgage rates. After soaring to 1.9 percent on Friday from a low of 1.47 percent earlier this month, the yield on the 10-year Treasury dropped back to 1.8 percent Wednesday.

“There’s still no good explanation for the large Treasury sell-off and increase in Treasury yields and mortgage rates of the prior weeks,” said Dick Lepre, senior loan officer at RPM Mortgage in San Francisco. “The liquidity intervention by the Fed could indicate that too few dollars were available. Dollars were tied up with provision for corporate taxes and issuance of a very significant amount of new Treasury debt. The question is this: Did we just see the end of the secular bull market for Treasurys? No one really knows.”, which puts out a weekly mortgage rate trend index, found more than three-quarters of the experts it surveyed expect rates to hold steady in the coming week.

“Economic data, ongoing trade-war chatter, geopolitical drama and tweets from the president all have been impacting rate swings this month,” said Jim Sahnger, mortgage planner for C2 Financial in Palm Beach Gardens, Fla. “The economic data has been overall rate negative while the other points have been all over the board. Look for rates to remain rangebound over the next week but expect the range to be broader than normal.”

Meanwhile, mortgage applications were flat as a bump in purchases was offset by a drop in refinances. According to the latest data from the Mortgage Bankers Association, the market composite index — a measure of total loan application volume — decreased 0.1 percent from a week earlier. The refinance index fell 4 percent, while the purchase index rose 6 percent.

The refinance share of mortgage activity accounted for 57.9 percent of all applications.

“The outlook this fall looks good for prospective home buyers," said Bob Broeksmit, MBA president and chief executive. "Borrowing costs are significantly lower than last year, single-family construction has increased for four straight months, and the healthy job market is boosting household confidence.”

Discover something new:

We’ve curated these stories to inspire your curiosity.

With a wetter and warmer climate, Lyme disease and ehrlichiosis could become more common as the number of tick bites increase.

Historically, men are more likely to work than women for myriad reasons. But the opposite is true of men and women in poverty.

Economists often disapprove of using government funds to build sports facilities. But baseball’s return to Washington has expanded the city’s tax base and spurred building in an overlooked part of town.