In the colonial period and into the 1800s parents and guardians generally required children to work. Initially most of the population worked in agriculture and children gradually moved into tasks demanding greater strength and skills as they aged. Craig (1993) uses census data to gauge the impact and value of child labor in the middle of the 1800s. He finds that the activities of farm-owning families were not closely linked to the number and ages of their children. Within each region, families in different life-cycle stages earned revenues in almost exactly the same manner.