U.S. mortgage rates maintain four-week lows

For the fourth consecutive week, U.S. mortgage rates stayed below 3.30 percent, according to Freddie Mac. The 30-year fixed mortgage rate averaged 3.24 percent for the week ending May 21 — down from 3.28 percent last week. A year ago, mortgage rates stood at 4.06 percent.  Low mortgage rates help propel U.S. home sales and the refinance market. “For the fourth consecutive week, the 30-year fixed-rate mortgage has been below 3.30 percent, giving potential buyers a good reason to continue shopping…