Freddie Mac announced on Friday that the average 30- and 15-year fixed-rate mortgages are now at their lowest since 1971, when the mortgage finance company started releasing their weekly surveys. The 30-year fixed-rate reached an average of 4.71 percent, compared to 5.53 percent this time last year. The 15-year fixed-rate, which set a record low the week prior, fell to 4.27 percent, compared to 5.77 percent this time last year.

ARMs have also fallen: one-year Treasury-indexed average ARMs dropped to 4.25 percent, the lowest in four years. The five-year hybrids, however, rose from the previous week to 4.19 percent, which is still significantly off the 5.77 percent this time last year. While the low rates make mortgages cheaper, it remains to be seen what overall effect they will have on residential real estate markets, since the tightening of credit continues.

The average for a 30-year jumbo loan has just fallen below 6 percent, according to research firm HSH’s Market Trends newsletter, to 5.96 percent. That is the lowest interest rate since September 2005. Meanwhile, the average conforming 30-year fixed-rate mortgage with no points averaged 5.9 percent last Wednesday, one of its lowest this year, while the overall average, which includes conforming, jumbo and agency jumbo for 30-year fixed rates, lost 0.06 percent, pulling HSH’s Fixed-Rate Mortgage Indicator (FRMI) to 5.35 percent, and the FRMI 5/1 Hybrid ARM dropped 0.07 percent to 4.67.

Whether that’s good news or a time to be wary remains to be seen: more high-end homeowners are undergoing foreclosures, according to the Wall Street Journal: 30 percent of foreclosures in June were on homes in top third tier of housing values, from 16 percent three years ago, while the bottom one-third is now only 35 percent of foreclosures, down from 55 percent in the the same timer period.

HSH seems to believe that things are improving in the private non-conforming mortgages, noting that “jumbos have sported a lower average rate in just 49 of the 509 weeks which have elapsed since Y2K — and that the “bottom of the bottom” noted during that period was only about 40 basis points (.40%) below this week’s figure.”

BusinessWeek points out that appraisers are following more stringent standards, making it more difficult to get qualified large loans. Meanwhile, they cite data from the Mortgage Bankers Association that home purchase prices are up 13 percent, and 18 percent for refinances. It’s a mixed bag, but maybe lightening up with better news soon.