The first wave came in the 1960s and early 1970s, led by governments trying to reduce the disinvestment that was taking place in inner-city urban areas. Additionally, starting in the 1960s and 1970s, U.S. industry has created a surplus of housing units as construction of new homes has far surpassed the rate of national household growth. However, the market forces that are dictated by an excess supply cannot fully explain the geographical specificity of gentrification in the U.S., for there are many large cities that meet this requirement and have not exhibited gentrification.