出生率
Birth rates ranging from 10 to 20 births per 1,000 are considered low, while rates from 40 to 50 births per 1,000 are considered high. There are problems associated with both extremes. High birth rates may stress government welfare and family programs, and more importantly store up overpopulation for the future. Additional problems faced by a country with a high birth rate include educating a growing number of children, creating jobs for these children when they enter the workforce, and dealing with the environmental impact of a large population. Low birth rates may stress the government to provide adequate senior welfare systems and stress families who must support the elders themselves. There will be fewer children (and a working-age population) to support an aging population.