In a time of 4 percent mortgages and programs like HARP designed to help homeowners refinance at lower rates, more than 15 million homeowners who are underwater on their mortgages are paying rates higher than 5 percent.

The latest data from CoreLogic reports that 45 percent of all borrowers have mortgages with a loan-to-value ratio greater than 80 percent, and 69 percent of those mortgages have above-market interest rates of 5 percent or more. Conversely, only 54 percent of borrowers who have less than 80 percent LTV have above-market interest rates.

Lenders generally refuse to refinance borrowers who are underwater, or close to it. The new HARP program introduced last month-after the period covered by the CoreLogic report-eliminated the requirement for a 125 percent loan-to-value ratio to make it easier for borrowers who are underwater or close to it to refinance. However, like the original HARP program, the new version is limited to those borrowers whose mortgages are held by either Fannie Mae or Freddie Mac-about half or all borrowers.

Refinancing at lower rate would reduce monthly payments and allow many borrowers to reduce their principal, which would strengthen their financial situation.

CoreLogic’s third quarter report on negative equity showed that 10.7 million, or 22.1 percent, of all residential properties with a mortgage were in negative equity at the end of the third quarter of 2011. This is down slightly from 10.9 million properties, or 22.5 percent, in the second quarter. An additional 2.4 million borrowers had less than 5 percent equity, referred to as near-negative equity, in the third quarter. Together, negative equity and near-negative equity mortgages accounted for 27.1 percent of all residential properties with a mortgage nationwide in the third quarter, down from 27.5 percent in the previous quarter.

Negative equity, often referred to as “underwater” or “upside-down,” is the condition in which borrowers owe more on their mortgages than their homes are worth. Negative equity can occur because of a decline in value, an increase in mortgage debt or a combination of both.

“Although slightly down, negative equity remains very high and renders many borrowers vulnerable when negative economic shocks occur, such as job loss or illness. The nearly $700 billion mortgage debt overhang has touched many corners of the market, and this overhang is holding back the recovery of the housing market and broader economy,” said Mark Fleming, chief economist with CoreLogic.

Nevada has the highest negative equity percentage with 58 percent of all of its mortgaged properties underwater, followed by Arizona (47 percent), Florida (44 percent), Michigan (35 percent) and Georgia (30 percent). This is the first quarter that Georgia entered the top five, surpassing California which had been in the top five since tracking began in 2009.

The top five states combined have an average negative equity ratio of 41.4 percent, while the remaining states have a combined average negative equity ratio of 17.6 percent.