How does energy efficiency improve over time?

Energy efficiency improves when our economies grow and our technologies get better. Examples of improving energy efficiency include requiring less petrol to drive the same number of kilometers; improving the thermal efficiency of a power plant to generate more electricity with less fuel; step-wise substitutions towards more energy-efficient technologies (such as the transition from kerosene to incandescent bulbs to compact fluorescents and LEDs); and the general, long-term path of economic growth from more energy-intensive sectors (such as agriculture and industry) towards less energy-intensive sectors (services and knowledge).