CoreLogic estimates that 22.3 percent of all residential properties with a mortgage were worth less than what was owed on their mortgages at the end of June, down from 23.7 percent at the end of March.
That translates into 10.8 million homeowners who owed more than their homes were worth at the end of June, down from 11.4 million at the end of March and 12.1 million at the end of 2011, CoreLogic said.
"Surging home prices this spring and summer, lower levels of inventory, and declining REO sale shares are all contributing to the nascent housing recovery and declining negative equity," CoreLogic Chief Economist Mark Fleming said in a statement.
Nevada had the highest percentage of mortgaged properties that were underwater (59 percent), followed by Florida (43 percent), Arizona (40 percent), Georgia (36 percent) and Michigan (33 percent).
Those five states accounted for 34.1 percent of the $689 billion of negative equity in the U.S.