people worldwide are at these lower rungs, depending on biomass fuels—crop waste, dung, wood, leaves, etc.—and coal to meet their energy needs. A disproportionate number of these individuals reside in Asia and Africa: 95% of the population in Afghanistan uses these fuels, 95% in Chad, 87% in Ghana, 82% in India, 80% in China, and so forth. As incomes rise, we would expect that households would substitute to higher quality fuel choices. However, this process has been quite slow. In fact, the World Bank reports that the use of biomass for all energy sources had remained constant at about 25% since 1975." Units of Analysis Domestic energy poverty Domestic energy poverty refers to a situation where a household does not have access or cannot afford to have the basic energy or energy services to achieve day to day living requirements. These requirements can change from country to country and region to region. The most common needs are lighting, cooking energy, domestic heating or cooling. Other authors consider different categories of energy needs from "fundamental energy needs" associated to human survival and extremely poor situations. "Basic energy needs" required for attaining basic living standards, which includes all the functions in the previous (cooking, heating and lighting) and, in addition energy to provide basic services linked to health, education and communications. "Energy needs for productive uses" when additionally basic energy needs the user requires energy to make a living; and finally "Energy for recreation", when the user has fulfilled the previous categories and needs energy for enjoyment." Until recently energy poverty definitions took only the minimum energy quantity required into consideration when defining energy poverty, but a different school of thought is that not only energy quantity but the quality and cleanliness of the energy used should be taken into consideration when defining energy poverty. One such definition reads as: "A person is in 'energy poverty' if they do not have access to at least: (a) the equivalent of 35 kg LPG for cooking per capita per year from liquid and/or gas fuels or from improved supply of solid fuel sources and improved (efficient and clean) cook stoves and (b) 120kWh electricity per capita per year for lighting, access to most basic services (drinking water, communication, improved health services, education improved services and others) plus some added value to local production An 'improved energy source' for cooking is one which requires less