If you spot a good rate and are shopping for a house or are open to a refinance, you may want to lock that rate ASAP.

This week's numbers

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Borrowers are getting great deals versus a year ago.

The average rate on a 30-year fixed-rate mortgage has fallen this week to 3.55%, from 3.60% last week, says mortgage giant Freddie Mac.

The loans in the survey come with an average 0.5 point.

At this time last year, the benchmark mortgage rate was almost an entire point higher, averaging 4.51%.

Rates have fallen so far that it might be worthwhile for homeowners to refinance — even a mortgage that's only a year old. Compare mortgage offers from multiple banks by visiting LendingTree.

"Households that refinanced in the second quarter of 2019 will save an average of $1,700 a year, which is equivalent to about $140 each month," says Sam Khater, Freddie Mac's chief economist.

Refinance applications rose 0.4% last week, says the Mortgage Bankers Association. Mortgage applications in general were down 0.9%.

Why rates are doing what they're doing

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Mortgage rates have resumed their slide.

After holding steady last week, mortgage rates have resumed their slide following recent drops in the interest rates on longer-term U.S. Treasury bonds.

Are you thinking about selling your home? It's an excellent time for that, Khater says.

"The drop in mortgage rates continues to stimulate the real estate market and the economy," he says. "Home purchase demand is up 5% from a year ago and has noticeably strengthened since the early summer months."

Thirty-year mortgage rates have dropped substantially since the start of 2019, when Freddie Mac put the average at 4.51%.

The mortgage company's latest forecast looks for rates to average 4.1% during all of 2019. Next year is expected to bring just a slight increase: to an average 4.2%.

This week's other mortgage rates

Rates on 15-year mortgages — a popular option for refinancers — have dropped to an average 3.03%, from 3.07% last week.

A year ago, those short-term home loans were at 3.98%, on average, Freddie Mac says.

And, rates keep going down on 5/1 adjustable-rate mortgages, or ARMs, which are level for five years and then can "adjust" up (or down) each year.

The ARMs are currently being offered at an average initial rate of 3.32%, down from 3.35% last week. One year ago, the starter rates were at an average 3.82%.

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