Buffalo has the oldest housing stock in the nation, with the largest percentage (67%) of homes built before 1940. In Erie County in 2013 there were 275 cases of elevated lead levels in children. The City of Buffalo has three of five zip codes in state with worst lead poisoning levels and accounts for roughly 95% of county lead cases. As of 2008, 13%-22% of children in the City suffered from asthma. In 2006, the City received 7,460 calls regarding housing violations and 1,612 regarding violations at vacant houses.