A/RES/50/81 Page 7 welfare of society. States should therefore actively encourage young people and youth organizations, to participate actively in programmes, including educational programmes, and actions designed to protect, promote and enhance the environment; (i) Every State should take measures to develop the possibilities of education and employment of young people with disabilities; (j) Every State should take measures to improve the situation of young people living in particularly difficult conditions, including by protecting their rights; (k) Every State should promote the goal of full employment as a basic priority of its economic and social policies, giving special attention to youth employment. They should also take measures to eliminate the economic exploitation of children; (l) Every State should provide young people with the health services necessary to ensure their physical and mental well-being, including measures to combat diseases such as malaria and HIV/AIDS, and to protect them from harmful drugs and the effects of addiction to drugs, tobacco and alcohol; (m) Every State should place people at the centre of development and should direct their economies to meet human needs more effectively and to ensure that young people are active participants and beneficiaries in the process of development. II. DEVELOPMENT SETTING 9. In 1995, the world youth population - defined by the United Nations as the age cohort 15-24 - is estimated to be 1.03 billion, or 18 per cent of the total world population. The majority of the world youth population (84 per cent in 1995) lives in developing countries. This figure is projected to increase to 89 per cent by 2025. The difficult circumstances that people experience in many developing countries are often even more difficult for young people because of limited opportunities for education and training, viable employment and health and social services, and because of a growing incidence of substance abuse and juvenile delinquency. Many developing countries are also experiencing unprecedented rates of rural-urban migration by young people. 10. Apart from the statistical definition of the term "youth" mentioned above, the meaning of the term "youth" varies in different societies around the world. Definitions of youth have changed continuously in response to fluctuating political, economic and socio-cultural circumstances. 11. Young people in industrialized countries comprise a relatively smaller proportion of the total population because of generally lower birth rates and longer life expectancy. They comprise a social group that faces particular problems and uncertainties regarding its future, problems that relate in part to limited opportunities for appropriate employment. 12. Young people in all countries are both a major human resource for development and key agents for social change, economic development and technological innovation. Their imagination, ideals, considerable energies and vision are essential for the continuing development of the societies in which they live. Thus, there is special need for new impetus to be given to the design and implementation of youth policies and programmes at all levels. The ways in which the challenges and potentials of young people are addressed /...