 At the time, mixed race neighborhoods were considered unstable and the corresponding attitude towards lending came to be known as red-lining because of the color used on the maps to designate a high-risk neighborhood.Out of this work emerged the sector theory that replaced Ernest Burgess's concentric zone theory of urban morphology.Third, Hoyt refined the method of economic base analysis that enabled municipal and state governments to assess potential population growth based on the mix of basic and non-basic employment within their economies.