Introduction

The energy consumption in the United States increased from 32 quads in 1950 to 101 quads in 2009. One quad is equal to 1015 British thermal units (Btu). There was an increase in ef’ciency in the industrial sector, primarily due to the shock of the oil crisis of 1973. However, you must remember that correlation between GDP and energy consumption does not mean cause and effect. The oil crisis of 1973 showed that ef’ciency is a major component in gross national product and the use of energy.