About 15.7 million U.S. homeowners were underwater in the first quarter of 2012, according to Zillow’s Negative Equity Report released Thursday. This translates to about one-third, or 31.4 percent, of homeowners with a mortgage, an increase from 31.1 percent in the previous quarter and a decrease from 32.4 percent a year ago.

Yet, most underwater homeowners are current on their mortgages, with nine in 10 continuing to make their payments on time. Also, just 10.1 percent of underwater homeowners are more than 90 days delinquent, Zillow reported.

“While it was disappointing to see negative equity numbers remain so high, it is important to note that negative equity remains only a paper loss for the vast majority of underwater homeowners,” said Zillow Chief Economist Stan Humphries. “As home values slowly increase and these homeowners continue to pay down their principal, they will surface again.”

While negative equity is never beneficial for homeowners, a large percentage of underwater borrowers are at least wading in shallow waters. Nearly 40 percent of underwater homeowners owe between 1 and 20 percent more than their home is worth, and another 21 percent owe between 21 and 40 percent more than their home’s value.

However, when looking at the total amount of negative equity that exists when combining all underwater homeowners, the number is $1.2 trillion. Through the $25 billion multistate settlement, $10 billion was allotted to reduce principal for underwater homeowners, an amount analysts have said is not enough to make a dramatic impact on recovery.

Additionally, 2.4 million homeowners with mortgages owe more than double what their home is worth. In Las Vegas, nearly 90,000 homeowners owe double their home’s value.

On a state level, Nevada has the highest percentage of negative equity, with 66.9 percent of all homeowners with mortgages underwater. Other states with high percentages include Arizona (52.3 percent), Georgia (46.8 percent), Florida (46.3 percent) and Michigan (41.7 percent).

The metro areas with the the highest percentage of homeowners with underwater mortgages were Las Vegas (79 percent), Phoenix (55.5 percent), Atlanta (55.2 percent), Orlando (53.9 percent), and Riverside, California (53.4 percent).

The metro areas with the lowest percentage of homeowners dealing with negative equity were Pittsburgh (16.7 percent), New York (21.3 percent), Boston (22 percent), San Jose (22.7 percent), and Philadelphia (25 percent).

Zillow also included an interactive map of the data organized by counties.

The Zillow Negative Equity Report looks at current outstanding loan amounts for individual owner-occupied homes and compares them to those homes’ current estimated values. Loan data are provided by TransUnion. According to Zillow, this is the only report that uses current outstanding loan balances on all mortgages when calculating negative equity, as opposed to basing outstanding loan balances on the most recent loan on a property, such as the original loan amount at the time of purchase or refinance.