Falling mortgage rates spur refinancing  

Mortgage rates have fallen below 6 percent for the first time since 2005, and some lenders are offering even lower rates. Investment bank Bear Stearns estimates that about 37 percent of homeowners could refinance their mortgages as rates drop. But some homeowners won’t benefit. Many have a mortgage that is too big, a credit score that is too low or a home that has fallen too much in value.