Graph of the Day: Energy Returned on Energy Invested, 1930-2000
From The Oil Drum: 
By David Murphy Cutler Cleveland of Boston University has reported that the EROI of oil and gas extraction in the U.S. has decreased from 100:1 in the 1930’s to 30:1 in the 1970’s to roughly 11:1 as of 2000 (Figure 1). But beyond the fact that society receives currently around 11 barrels of oil for every 1 barrel that it spends getting that oil, What does this mean? First, it means that, if the trend of declining EROI continues, society will be spending an increasingly larger chunk of its remaining energy to get more energy. This cycle is positively reinforcing:
Declining EROI means that the net energy contained in each unit of energy delivered to society is decreasing over time, requiring the extraction of increasingly greater quantities just to meet societal demand → decreases the quantity of energy remaining in the ground for future society → makes it more difficult to find and develop the remaining bit of energy. …
The Net Hubbert Curve: What Does It Mean?
