The standard of living is a measure of economic welfare. It generally refers to the availability of scarce goods and services, usually measured by per capita income or per capita consumption, calculated in constant dollars, to satisfy wants rather than needs. Because the well-being that living standards are supposed to measure is an individual matter, per capita availability of goods and services in a country is a measure of general welfare only if the goods and services are distributed fairly evenly among people. If income distribution is very uneven, then despite high per capita availability of commodities, large numbers of persons may have a very low standard of living and others a very high standard - valid comparisons can be made only among reasonably homogeneous groups