The fifth of the Earth's population which lives in the developed countries consumes over four fifths of the commercial energy produced. On average, an inhabitant of a high-income country burns 15 times more energy than someone in a low-income country, and about four times more than someone in a middle-income country. Eighty-five percent of the commercial energy used worldwide comes from fossil fuels, but about 40% of humanity depend on non-commercial sources of energy such as fuelwood and agricultural residues, which only account for 12% of the world's energy use.
In 1994, OECD reported that there has been a general increase in total energy consumption of 30 percent over the past 20 years. By 2010, OECD countries are expected to be consuming 30 percent more energy and nearly 20 percent more oil than in 1990. Current (1995) energy consumption is 8-9 billion tonnes oil equivalent (toe) per annum. It has been estimated that this level will rise to 15 billion toe by 2050 bases on the assumptions of a population of 10 billion, a world economy eight times larger than in 1985 and an energy intensity per dollar GDP of one quarter.