5. Energy Intensity Declines Over Time

Though energy use has generally increased over time it has grown more slowly than has GDP. Globally it grew at about half the rate of GDP in the last 30 years. As a result energy intensity (energy per dollar of GDP) has declined globally:



Energy intensity has declined in most key countries. This chart shows the trends from 1971 to 2007:



Note that though China was very energy intensive in the 1970s, India was not. Hence there was not a lot of correlation between income per capita and energy intensity back then either. In fact (as Stephen Howes raised at my seminar on Tuesday) energy intensity has increased in some countries over time. These appear to be mostly in Latin America. We don't see this trend in any developed country. So it is a stylized but not universal fact that energy intensity has declined over time.

When we ignore traditional sources of energy such as biomass and animal power a very different pattern emerges:



As fossil fuel use was once zero in most countries (some countries have used coal for a very long time) energy intensity based on only modern energy sources must also have been zero and then increased. This results in an inverted U shape path as shown in this chart.