Mortgage rates remain on the decline, according to the latest survey from Freddie Mac.

Freddie Mac’s Primary Mortgage Market Survey showed that, for the week ending March 21, fixed mortgage rates remain below where they were a year ago.

Average 30-year fixed rates dropped from week to week, from 4.31 percent to 4.28 percent. Last year, 30-year rates averaged 4.45 percent.

The average for a 15-year fixed mortgage fell from 3.76 percent to 3.71 percent. A year ago at this time, 15-year rates averaged 3.91 percent.

“Mortgage rates have dipped quite dramatically since the start of the year and house prices continue to moderate, which should help on the homebuyer affordability front,” said Sam Khater, Freddie Mac’s chief economist. “The combination of improving affordability and more inventory than the last few spring selling seasons should lead to improved home sales demand.”

Five-year adjustable rate mortgage rates remained unchanged for the week at 3.84 percent. ARM rates are up from a year ago, when they were 3.68 percent.