factors that are likely to see oil production plateau. A 2008 Journal of Energy Security analysis of the energy return on drilling effort (energy returned on energy invested, also referred to as EROEI) in the United States concluded that there was extremely limited potential to increase production of both gas and (especially) oil. By looking at the historical response of production to variation in drilling effort, the analysis showed very little increase of production attributable to increased drilling. This was because of diminishing returns with increasing drilling effort: as drilling effort increased, the energy obtained per active drill rig in the past had been reduced according to a severely diminishing power law. The study concluded that even an enormous increase of drilling effort was unlikely to significantly increase oil and gas production in a mature petroleum region such as the United States. However, contrary to the study's conclusion, since the analysis was published in 2008, US production of crude oil has more than doubled, increasing 119%, and production of dry natural gas has increased 51% (2018 compared to 2008). The previous assumption of inevitable declining volumes of oil and gas produced per unit of effort is contrary to recent experience in the US. In the United States, as of 2017, there has been an ongoing decade-long increase in the productivity of oil and gas drilling in all the major tight oil and gas plays. The US Energy Information Administration reports, for instance, that in the Bakken Shale production area of North Dakota, the volume of oil produced per day of drilling rig time in January 2017 was 4 times the oil volume per day of drilling five years previous, in January 2012, and nearly 10 times the oil volume per day of ten years previous, in January 2007. In the Marcellus gas region of the northeast, The volume of gas produced per day of drilling time in January 2017 was 3 times the gas volume per day of drilling five years previous, in January 2012, and 28 times the gas volume per day of drilling ten years previous, in January 2007. New research estimates that the energy required to produce all petroleum liquids (not including transportation, refining and distribution) represents today the equivalent of 16% of this same production and by 2050, an amount equivalent to half of the gross energy production will be required. For gases, the energy needed