Most, but not all, authorities believe that Russia has the world's largest proven reserves of natural gas. Sources indicating Russia to have the largest proven reserves include the US CIA (47.6 trillion cubic meters),[6] the US Energy Information Administration (47.8 tcm),[7] and OPEC (48.7 tcm).[8] However, BP credits Russia with only 31.3 tcm as of 1 January 2014,[9] which would place it in second place, slightly behind Iran (33.1 to 33.8 tcm, depending on the source). In addition to having the world's largest proven reserves of natural gas, according to US Geological Survey estimations, Russia is also likely to have the world's largest volume of still-undiscovered natural gas: a mean probable volume of 6.7 trillion cubic meters.