 He claims a strong relationship exists between an area's allowance of building housing at higher density and racial integration between blacks and whites in the United States.The relationship between segregation and density is explained by Rothwell and Massey as the restrictive density zoning producing higher housing prices in white areas and limiting opportunities for people with modest incomes to leave segregated areas.Between 1980 and 2000, racial integration occurred faster in areas that did not have strict density regulations than those that did.