Zombie foreclosures, named for the undead nature of the home rather than its occupants, have become significantly less common since last year according to an analysis by the real estate data company RealtyTrac.

In its third quarter U.S. Zombie Foreclosure and Vacant Property Report, RealtyTrac determined that there were 20,050 residential properties in the United States that were in the foreclosure process but not yet repossessed by the lender. This total marked a 27 percent reduction from the previous quarter and a 43 percent decline from the third quarter of 2014.

Homes that are considered to be zombie foreclosures can have a depressing effect on property values in a neighborhood, and can also hold unpleasant surprises for the previous owner. In this type of foreclosure, the previous owner moves out in anticipation of a lender repossessing the home. The home becomes more deteriorated while it is vacant, and the previous owner may be stuck with costs such as property taxes and fines for failing to comply with housing codes.

This type of foreclosure is distinct from a "vampire foreclosure," in which a homeowner remains in a property after it has been foreclosed. A lender cannot advertise the home for sale while it is occupied, but will likely pursue eviction of the previous owner when it decides to put the property on the market.

RealtyTrac says there were 1.5 million vacant residential properties in the United States in the third quarter, accounting for 1.8 percent of all homes in the nation. A total of 36.5 percent of the vacant properties—547,846 in total—had at least one open loan; 6.2 percent—or 92,790—were considered seriously underwater, with loans that exceeded the home's value by at least 25 percent. The remaining 1.45 million vacant homes were considered to be non-distressed.

Zombie foreclosures accounted for only 1.3 percent of all vacant U.S. homes. There were a total of 27,980 real estate owned properties, or those owned by the bank, which made up 1.9 percent of all vacant homes at the end of the third quarter.

"The overall inventory of homes in the foreclosure process has dropped 36 percent over the past year so it's not too surprising to see a similarly dramatic drop in vacant zombie foreclosures," said Daren Blomquist, vice president at RealtyTrac. "What is surprising is there are so many vacant homes where the homeowners do not appear to be in financial distress — with only 3 percent in foreclosure or bank owned, and only 6 percent that are underwater. More than 63 percent of these vacant homes are not even encumbered by a loan, owned free and clear by the owner. The fact that the homeowners are not selling given the recovering real estate market in most areas indicates that many of these properties are in poor condition and in neighborhoods that have been left behind by the housing recovery."

New Jersey had the highest number of zombie foreclosures with 3,997, and it also had the highest share of zombie foreclosures as a percentage of total vacancies at 9.4 percent. New Jersey was also one of six states with an increase in zombie foreclosures from last year, with the number going up 29 percent. Massachusetts had the most significant increase at 66 percent.

Other states with a large number of zombie foreclosures included Florida (3,512), New York (3,365), Illinois (1,187), and Ohio (1,028). Zombie foreclosures made up the second highest share of vacancies in New York, accounting for 8.2 percent of all empty homes. This state was followed by Nevada (2.7 percent), Massachusetts (2.5 percent), and Illinois (2.1 percent).

Among the 147 metropolitan statistical areas with at least 100,000 residential properties, New York City had the most zombie foreclosures with 3,531 – more than twice as many as Philadelphia, which had the next highest number at 1,610. Chicago's zombie foreclosures totaled 989, Tampa had 984, and Miami had 866.

New York City was one of the metro areas with the highest percentage of zombie foreclosures at 10 percent, but Rochester, N.Y., had the largest share at 14.3 percent. Other metro areas where zombie foreclosures made up a large share of vacant residential properties included Trenton, N.J. (10.5 percent), Albany, N.Y. (7.9 percent), and Allentown, Pennsylvania (5.2 percent).

Twenty-one major metro areas had a year-over-year increase in zombie foreclosures. These cities included Boston (up 61 percent), Worcester, Mass. (up 43 percent), St. Louis (up 16 percent), Philadelphia (up 15 percent), and Trenton (up 11 percent).

When RealtyTrac considered vacant residential properties as a whole, Florida had the most with 180,846. Other states with a large number of vacancies included Michigan (117,833), Texas (117,350), Ohio (86,416), and California (80,750).

Vacant properties in Michigan made up the largest share of all residences at 3.9 percent, followed by Indiana with 3 percent. Vacant homes made up 2.8 percent of the residential properties in Mississippi, 2.7 percent of those in Florida, and 2.6 percent of those in Alabama.

Michigan also had a large number of vacancies in its cities. Detroit was the metro area with the largest number of vacancies at 84,291. Vacancies in this city accounted for 5.5 percent of all residences, second only to the share of 7.5 percent share in Flint.

Miami had the second highest number of vacancies at 67,139, followed by Chicago (48,181), Atlanta (36,396), and New York City (35,200). Other metro areas with a high percentage of vacancies included Youngstown, Ohio (4.4 percent), Beaumont-Port Arthur, Texas (4.2 percent), and Atlantic City, N.J. (4.1 percent).

In Connecticut, RealtyTrac calculated that there were 3,005 vacant properties in the Hartford metro area. These vacancies made up 0.8 percent of all residential properties. A total of 7.7 percent were underwater, and 0.3 percent were foreclosures.

Of the 2,959 vacancies in the New Haven metro area, 9.7 percent were underwater on their loans. A total of 1.2 percent of the homes in the city were vacant, and 0.4 percent were considered zombie foreclosures.

There were 1,779 in the Bridgeport metro area, accounting for 0.7 percent of all residences. Zombie foreclosures accounted for 0.5 percent of the city's properties, and 8 percent of the vacant residences were underwater on their loans.

Florida had the most vacant homes that were considered to be seriously underwater at 16,723, followed by Ohio (9,237), Illinois (7,397), New Jersey (6,306), and California (5,187). The states with the highest share of underwater vacant homes were New Jersey (14.9 percent), Maryland (13.1 percent), Illinois (12.9 percent), Nevada (11.7 percent), and Ohio (10.7 percent).

Chicago was the metro area with the most seriously underwater vacant homes, with 6,638 properties included in this designation. Other cities with a large number of seriously underwater empty residential properties were Miami (5,546), New York City (3,952), Detroit (3,739), and Cleveland (3,488).

Trenton had the highest share of underwater vacant homes at 21.4 percent. This city was followed by Columbus, Ohio (19.1 percent), Cleveland (17.2 percent), Fresno, Calif. (16.5 percent), and Atlantic City (15.2 percent).

South Dakota had the lowest percentage of vacant properties at 0.3 percent. New Hampshire had 0.4 percent, North Dakota and Vermont had 0.5 percent, and Montana had 0.8 percent.

San Jose, California, and Fort Collins, Colorado, had the lowest share of vacant residential properties at 0.3 percent. Other metro areas with a low percentage of empty homes included Manchester, N.H.; Lancaster, Penn.; and Fayetteville, Arkansas, each with 0.4 percent.

RealtyTrac matched its records database, which includes almost 85 million residences, to address-level data from the U.S. Postal Service to identify properties where no one was picking up mail. Homes where mail was forwarded to a new address were not included. The analysis also used foreclosure documents and mortgage data in the public record as well as estimated market values.