Rates for 30-year mortgages hit an all-time low the week ended April 30. Since then, rates have hovered near 5%, spurring refinancing activity and home sales.

However, credit standards remain stringent, so the best rates usually are available only to borrowers with solid credit and a 20% down payment.

The Federal Reserve has pumped $1.25 trillion into mortgage-backed securities to try to lower rates on mortgages and loosen credit availability. Rates on 30-year mortgages traditionally track yields on long-term government debt.