The average rate on a 15-year fixed-rate mortgage fell in the week ending April 25. Freddie Mac reported the average rate fell from 2.64% last week to 2.61% this week. It was the lowest rate since Freddie Mac has been keeping track of these records in 1971. A year ago, the average rate was 3.12%.

The five-year adjustable-rate mortgage also fell to an all-time low — from 2.6% last week to 2.58% this week. It was the lowest rate since that mortgage product was available in 2005.

Freddie Mac’s chief economist, Frank Nothaft, said that the record-low rates have boosted home sales. He points out that existing home sales averaged an annual pace of 4.9 million the first three months of 2013 (the most since the fourth quarter of 2009) and new home sales in Q1 2013 were at 424,000 — the strongest since Q3 2008.

Meanwhile, the average rate on a 30-year fixed-rate mortgage fell slightly to 3.40%, compared to 3.41% the previous week. The one-year ARM also had a slight downturn from 2.63% last week to 2.62% this week.