The continuing growth of home prices stoked a long-running trend of increasing equity in the fourth quarter of 2017 and helped pull more properties out of "underwater" situations, according to the property analytics company CoreLogic.

The year-end report found that homeowners in the United States gained a cumulative total of $908.4 billion in equity in 2017, a year-over-year increase of 12.2 percent. CoreLogic also noted that homeowner equity has more than doubled since the last quarter of 2012, increasing $4.5 trillion in that five-year period.

"Home price growth has been the primary driver of home equity wealth creation," said Frank Nothaft, chief economist at CoreLogic. "The CoreLogic Home Price Index grew 6.2 percent during 2017, the largest calendar year increase since 2013. Likewise, the average growth in home equity was more than $15,000 during 2017, the most in four years. Because wealth gains spur additional consumer purchases, the rise in home equity wealth during 2017 should add more than $50 billion to U.S. consumption spending over the next two to three years."

While none of the 45 states with available data had a year-over-year decrease in average home equity in the fourth quarter, gains varied considerably by state. Frank Martell, president and CEO of CoreLogic, said the stronger gains typically occurred in areas with a limited number of homes for sale as well as robust appreciation in values.

The West Coast continued to have the strongest equity growth, led by an average annual increase of $44,500 in California. This was followed by average equity growth of $40,000 in Washington and $27,000 in Nevada and Utah.

Louisiana had the least significant change in equity, with values remaining relatively unchanged from the end of 2016. Oklahoma homeowners saw an average equity gain of $2,000, while those in Alaska gained $3,000 in equity on average.

In Connecticut, the average homeowner saw their equity increase by $4,000. Rhode Island residences had an average equity gain of $20,000.

The report found that a total of 4.9 percent of U.S. homes—2.5 million residences—were underwater, or experiencing negative equity, in the fourth quarter of 2017. In this situation, the combined total of outstanding loans on the property is greater than the fair market value of the home.

The negative equity share was down from 6.3 percent in the fourth quarter of 2016 and a high of 26 percent in the fourth quarter of 2009. Approximately 675,000 properties regained equity in 2017.

The aggregate total of negative equity in the United States stood at $283.1 billion at the end of 2017. This was up 2.1 percent from the third quarter of the year, but also marked a year-over-year decrease of 1.1 percent.

Negative equity shares remained high in several states. A total of 10.4 percent of homes in Louisiana were worth less than their mortgages, along with 8.9 percent of Illinois homes and 8.5 percent of Florida and Connecticut residences.

Three states had a slight increase in negative equity from the fourth quarter of 2016. The share of underwater homes was up 0.8 percentage points in New York, 0.2 percentage points in Louisiana, and 0.1 percentage points in Oklahoma.

Nevada had a decrease of 5.5 percentage points in its negative equity share to 8 percent, the strongest drop in the nation. The state also had the most significant decrease from its peak negative equity share, which stood at 72.7 percent in the first quarter of 2010.

Looking at 10 major metropolitan areas, CoreLogic found that negative equity shares continued to improve but remained high in some markets. The areas with the highest share of underwater homes included Miami (13.1 percent), Chicago (10.1 percent), and Las Vegas (9.2 percent).

CoreLogic uses a database of more than 50 million properties, which it says represent 95 percent of all mortgaged homes in the United States, to develop its reports. The equity reports focus only on properties with outstanding mortgages, which make up approximately 63 percent of residences in the United States.

The company's reports have consistently differed from ATTOM Data Solutions, another property analytics company which issues quarterly equity reports. Both companies say negative equity has been decreasing, but ATTOM Data Solutions has determined that a larger share of the 150 million homes in its database is underwater.

In its report for the third quarter of 2017, the company determined that approximately 4.6 million U.S. homes had outstanding loans which were at least 25 percent more than their value. It determined that these properties represented 8.7 percent of all mortgaged homes in the nation. ATTOM Data Solutions has not yet issued a fourth quarter report.