The number of Americans who owe more on their mortgages than their homes are worth fell at the fastest pace on record in the third quarter as prices rose, real estate research firm Zillow Inc. said, Bloomberg reported. The percentage of homes with mortgages that had negative equity dropped to 21 percent from 23.8 percent in September. The number of owners with at least 20 percent equity climbed to 60.8 percent from 58.1 percent.