Consumer demand for some commodities does not rise as incomes rise (the per capita income elasticity of demand is low in the richer countries). In some cases, most notably with cereals as a source of food calories, rising standards of living tend, in high-income countries, to reduce per capita consumption to the point of offsetting the effects of population growth (which tends to be slow in such countries). This phenomenon leads to an unusually slow increase in demand for the primary commodities produced by the developing countries.