dependency ratio
3.The age dependency ratio - the ratio of the young and the aged to people of age 15 to 64 - dropped from 438 per 1000 in 1987 to 398 per 1000 in 1997.
4.In the advantageous historical period with a decreasing birth rate and a declining total social dependency ratio and rich labor resource, it is essential to develop education, science and technology in a big way, expand social input, and raise the accumulation level. Thus China will lay a solid foundation for speeding up economic development, strengthening its overall national power, and realizing the goal of a coordinated and sustained development of population, economy, society, resources and environment.
5.Then the Delphi technique and principal components analysis are used to choose six factors from the system to form a new integrated index-degrees of petroleum security. The six factors are the domestic crude oil reserve-production ratio, the domestic crude oil reserve replacement ratio, dependency of domestic petroleum consumption on import, concentration ratio of domestic petroleum imports, international crude oil prices and domestic petroleum reserve storage level.
