There have been impressive real energy efficiency gains since 1973. However, the change from an industrial to an information economy has also boosted the BTU/GDP ratios. A lot of the energy-consuming manufacturing has been out-sourced to other countries, while low-energy-consumption services have grown.
True, although much of the gain was from better insulation of houses and buildings, and much improved fuel-efficiency for cars.
Information technology also has contributed greatly. (Remember when you had to physically send letters? Go shopping to compare prices? Buy a newspaper to get your news?)