As of April 2012, 1.5 million homes are in shadow inventory, which is a 14.8 percent decrease from last year in April when the number of homes hiding in the shadows was 1.8 million, CoreLogic reported Thursday.

The current level of shadow inventory is at the lowest since October 2008 and represents a supply of four months compared to a supply of 6 months a year ago.

CoreLogic counts shadow inventory, also known as pending supply, by calculating the number of distressed properties that are seriously delinquent, in foreclosure, and held as real estate owned (REO) by servicers, but not currently listed on multiple listing services.

“Since peaking at 2.1 million units in January 2010, the shadow inventory has fallen by 28 percent. The decline in the shadow inventory is a positive development because it removes some of the downward pressure on house prices,” said Mark Fleming, chief economist for CoreLogic. “This is one of the reasons why some markets that were formerly identified as deeply distressed, like Arizona, California and Nevada, are now experiencing price increases.

Out of the 1.5 million properties counted as shadow inventory, most are in the seriously delinquent category. With 720,000 seriously delinquent properties, this represents a supply of two months. About 410,000 are in some stage of foreclosure, a supply of 1.1 months, and 390,000 are already in REO, also a supply of 1.1 months.

States with the highest decrease in serious delinquencies, which are the main driver of the shadow inventory, were Arizona (-37.0 percent), California (-28.0 percent), Nevada (-27.4 percent), Michigan (-23.7 percent) and Minnesota (-18.1 percent).

The actual dollar amount of shadow inventory as of April 2012 was $246 billion, down from $270 billion a year ago and a three-year low.