One of the focal points of the debate is the prospect for meeting food demand in China. Lester Brown has concluded that rapid industrialization will lead to a substantial withdrawal of land from agriculture and a major growth in dependence on food imports. Food demand is a function of population size, the income available to that population through gross domestic product, and the share of income spent on food. In the key long-term loop, prices help determine whether there are apparent profits to be made in food production and thus whether capital investments will be made. Price changes affect demand itself, but food is so essential to human well-being that the responsiveness of food demand to prices is not terribly great. In the most basic terms, food production depends on the amount of land under cultivation and the productivity of that land. Governments and voluntary organizations also sometimes turn to food aid for countries in special need.