Homeowners walking away from underwater mortgages

`` As property values have plummeted by an average of 50 percent, such strategic defaults now make up a sizable chunk of South Florida's foreclosures. In the fourth quarter of last year, they accounted for an estimated 28 percent of all defaults in Miami-Dade and Broward counties, according to recent research from the credit bureau Experian and Oliver Wyman, a New York-based international consulting firm.''