This book focuses on the evolution of energy-using activities in a dozen industrialized countries and many developing countries as well, with particular attention paid to the energy-intensive branches of manufacturing, automobiles, air travel, home heating, and electric appliances. The authors draw scenarios of future energy efficiency improvements, based on their findings about past improvements, and their survey of the potential for change. The study concludes that only massive improvement in energy efficiency in the near and medium term can provide the world with breathing room to develop and deploy a mix of relatively clean energy sources that will not further aggravate environmental or climate problems.