In 2006, Benjamin Koellmann bought a condominium in Miami Beach. By his calculation, it will be about the year 2025 before he can sell his modest home for what he paid. Or maybe 2040.

“People like me are beginning to feel like suckers,” Mr. Koellmann said. “Why not let it go in default and rent a better place for less?”

After three years of plunging real estate values, after the bailouts of the bankers and the revival of their million-dollar bonuses, after the Obama administration’s loan modification plan raised the expectations of many but satisfied only a few, a large group of distressed homeowners is wondering the same thing.

New research suggests that when a home’s value falls below 75 percent of the amount owed on the mortgage, the owner starts to think hard about walking away, even if he or she has the money to keep paying.