A major objective of development is the growth of per capita income in the developing countries, as one of the means to improve living conditions and reduce international disparities in income and wealth. Further, the inadequacy of housing, and the lack of basic amenities such as drinking water and sanitation, not only affect the quality of life but also the rates of morbidity and mortality. An improvement in quality of life requires not only population policies, but also programmes to improve nutritional intake, provide new and renewable sources of energy, and to improve living conditions. While there is probably no single index of the level of living that can be applied in internationally, there are four recognized demographic variables associated with a better quality of life: longer life expectancy, lower mortality rates for all age groups of the population, lower morbidity rates, and lower fertility rates.
Income or output per capita is generally taken as the main indicator of the quality of life. In 1981 the per capita income of the richest country was nearly 220 times that of the poorest country and under present growth trends, international disparities will almost certainly widen. At present growth rates, it will take 70 to 90 years for the poorest countries to double their per capita income; even this will only slightly improve their standards of living. Meanwhile, their populations will double in 35 years or less.