Notes: While the CDC EPHTN tracks only radon measurements pre and post-mitigation, the US EPA estimates the number of homes built with radon resistant features through the Home Innovation Research Labs’ Builder Practices Reports, which  are based on data obtained through the Annual Builder Practices Survey (ABPS), a nationally disseminated survey of home builders. The resulting data are tabulated using a robust methodology that includes balancing by geographic and demographic variables to provide an accurate picture of the characteristics of homes built during the calendar year.  