This seems to suggest that there is some sort of 'boomerang' effect in which the least wealthy (least productive) countries generate the greatest economic return on energy consumed, i.e. the poorest seem to be the most highly energy efficient. Increasing wealth seems to be related to a reducing return on energy employed until reaching those countries where individuals are at least moderately wealthy (productive) at which point increasing wealth is associated with an increasing return on energy consumed.
Rather than a real effect is it possible that the 'boomerang' is caused by some artefact of the data being analysed? Wood is omitted from most energy budgets and this can be a major source of energy in some economies. For example, consider the USA from 1790 to 2006:
Once wood is accounting for it seems that the boomerang effect disappears and the US has been steadily increasing individual wealth while improving energy effectiveness, i.e. increasing the return on energy consumed.
What about a country like Bangladesh?
It seems that once wood is included in the energy consumption Bangladesh is not quite so highly energy efficient as we might have thought. Not only that but it exhibits the same trend of increasing individual wealth with improving the return on energy consumed.
So the poorest countries do not achieve the greatest return on energy consumed; increasing individual wealth is instead associated with increasing efficiency of energy use!
