"A deeper law than Moore's?" - The energy efficiency of computing is doubling every 18 months. | Intel co-founder Gordon Moore states that personal computer performance doubles every 1.5 years. | “Koomey's Law" (Stanford) closely follows this & states that electronic energy efficiency doubles every 1.5 years | October 10th 2011 by The Economist
The entire article in The Economist is very interesting. A bit tendentious, but appropriately gloomy if you see this figure. Note, of the 3 European newcomers in the last 30 years, only 1 hails from the continent.