Growing up in a smoke-free home is now the overwhelming norm for most Americans, with the share of smoke-free homes nearly doubling in the 20 years that ended in 2011, the Centers for Disease Control and Prevention said today in a new study. Overall, the prevalence of smoke-free home rules increased from 43 percent during 1992—1993 to 83 percent during 2010—2011, according to the study, which appears in today's Mortality and Morbidity Weekly Report, published by CDC.