The city's unique density, encouraged by much of it being surrounded by water, facilitates the highest rate of mass transit use in the United States. New York is one of the most energy efficient cities in the United States as a result. Gasoline consumption in New York is at the rate the national average was in the 1920s. The city's mass transit system, multifamily housing, mixed neighborhoods and the fact that greenfield land is no longer available to development, make building in New York very energy efficient. New York City has a larger population than all but eleven states, and consumes less energy per-capita than any. The average New Yorker consumes a little more than half of the electricity of someone who lives in Chicago and nearly one-quarter the electricity consumed by someone who lives in Dallas.