Manhattan is becoming an island of extremes.

The mean income of the top 5 percent of households in Manhattan soared 9 percent in 2013 over 2012, giving Manhattan the biggest dollar income gap of any county in the country, according to data from the Census Bureau.

The top 5 percent of households earned $864,394, or 88 times as much as the poorest 20 percent, according to the Census Bureau’s American Community Survey, which is being released Thursday and covers the final year of the Bloomberg administration.

“The recovery seems to be going to those at the top, much more than those in the middle, while those at the bottom may even be losing ground,” said Andrew A. Beveridge, a sociologist at Queens College of the City University of New York. He attributed the disparity to the surging costs of housing and the lack of housing subsidies and other forms of public assistance available to many needy families.