Rural vs. urban areas. Seven incidence studies were performed in urban areas (50%), five in rural areas (36%), and two (14%) in both urban and rural areas. Pneumonia incidence rates were generally higher in rural areas compared with urban areas (Table S2) . For example, a study in Guangdong that compared pneumonia rates in both rural and urban settings found that rates in rural areas were more than four times higher than urban rates in children ,1 year of age (0.91 vs. 0.19 episodes per person-year, respectively) and more than six times higher in children ,5 years of age (0.79 vs. 0.12 episodes per person-year, respectively) [24] .