MDCs were the first to urbanize, shifting toward industry and moving into cities (stage 2 or 3 of the demographic transition model). Historically, MDCs were the urbanized ones, while LDCs remained non developed agricultural areas. Today, MDCs are postindustrial, meaning that people are moving back into suburbs and working in tertiary, quaternary, and quinary economic sectors, and having manufacturing and manual labor done elsewhere. LDCs are rapidly developing, and industrializing.