Driven by the news that the The Federal Reserve plans to spend an additional $750 billion to buy mortgage-backed securities, the weekly average rate borrowers were quoted on Zillow Mortgage Marketplace for thirty-year mortgages fell to 5.06 percent, down from 5.21 percent the week prior, according to the Zillow Mortgage Rate Monitor, compiled by real estate Web site Zillow.com(R).

Meanwhile, rates for 15-year fixed mortgages dropped to 4.73 percent, down from 4.78 percent and 5-1 adjustable rate mortgages also fell, down to 4.69 percent from 4.71 percent the week prior.

Rates for 30-year fixed purchase mortgages had decreased slightly on Monday evening, with the average rate on Zillow Mortgage Marketplace at 5.03 percent.

Thirty-year fixed mortgage rates varied by state. Illinois mortgage rates, Michigan mortgage rates and Wisconsin mortgage rates decreased the most, dropping from 5.30 percent to 5.12 percent in Illinois, from 5.27 percent to 5.09 percent in Michigan and from 5.33 percent to 5.15 percent in Wisconsin. Georgia mortgage rates (4.92%), California mortgage rates (5.02%), Pennsylvania mortgage rates (5.02%) and Texas mortgage rates (5.02%) were the lowest in the country while Ohio mortgage rates (5.20%) were the highest.