Rates on 30-year mortgages tied a record low this week, spurring refinancing activity as the troubled housing market moves closer to possibly hitting the bottom, Freddie Mac said Thursday.

Average rates on 30-year fixed mortgages, the most popular loan among home buyers, slid to 4.78 percent from 4.8 percent last week, mortgage giant Freddie Mac said. Last year at this time, the average rate on a 30-year mortgage was 6.06 percent.

The all-time low of 4.78 percent was recorded the week of April 2. Freddie Mac’s annual survey dates back to 1971.

Low mortgage rates have led to more refinancing activity since rates first fell dramatically in the winter. Rates slid again after the Federal Reserve said last month that it would buy $1.2 trillion in mortgage-backed securities and $300 billion in long-term government debt, which traditionally influences rates on 30-year home loans.

Frank Nothaft, Freddie Mac’s chief economist, said the low rate means that those who refinance a $200,000 loan would save almost $212 in monthly mortgage payments and more than $2,500 per year.