Middle class housing affordability continues to slip, according to a newly-released study.

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In general, the study from real estate researcher Trulia.com said rising home prices and stagnant incomes are moving the American Dream a little farther away from the grasp of the middle class.

"Across the country, I think the main thing is that home prices are rising and mortgage rates are rising as well," said Trulia's Daisy Kong, "and so that's increasing the cost of home ownership across the board."

The study said middle class affordability dropped 6 percent in parts of North Jersey in the past year, 8 percent in some Central Jersey areas and 5 percent in parts of South Jersey.

The affordability picture is also bleak in many other parts of the country. In 20 of the nation's top 100 metropolitan areas, according to the study, buying a house was out of reach for middle class families. The average monthly home payment is up 20 percent this year as compared to 2013.

Trulia defines home affordability and the ability of families to buy a house as monthly costs -- after a 20 percent down payment -- that include the mortgage, insurance and property taxes amounting to less than 31 percent of the median household income in that particular region.

For more information about the study, go to Trulia.com.