4. DATA SOURCESCDPH has two been collecting key data sources that form the basis of our predictions:1. Blood Lead Level Tests: We were given the re-sults of all 2.5 million BLL tests conducted in Chicago from 1993 through 2013. This corresponds to roughly 1 million children (see Section 5 for record linkage),with about 40,000 children born in the city every year and an average of 2.5 tests per child. Clinics submit the BLL test results to the Illinois Department of Pub-lic Health (IDPH) and IDPH transfers the results toCDPH daily.2.Home Lead Inspection Records:We were also given 120,000 home-inspection records from the sametime period (1993-2013).These reports detail the in-spector's fidings when they are sent to a home sus-pected of being hazardous. The most important en-tries in our model are those corresponding to the date of a house's initial inspection and the date at which it was deemed to be in compliance with lead-safetystandards.