"The United States has large reserves of all the mineral fuels. In round numbers. the geologically inferred coal reserves in the United Slates are estimated at 3.1 trillion tons. This amount is probably 40 percent of the worlds reserves of all ranks of coal. As of December 31, 1947 the proved reserves of crude oil (21.5 billion barrels) plus natural-gas liquids (3 .2 billion barrels) were estimated at 24 billion barrels and of natural gas a 166 trillion cubic feet. The United States petroleum reserves are about 1/3/of all the worlds reserves. No data are available on world natural gas reserves. The estimate of recoverable oil from oil shale in the United States has recently been increased to about 200 billon barrels."