These phrases refer to the price ratio between natural gas and crude oil. Over the years, the ratio of oil to gas market prices has averaged about 9 since 1990, which is to say that the price per unit of oil is usually about 9 times more than the price per same unit of natural gas.

When crude oil is $100 a barrel this is equivalent to $17.2 an mmbtu, which is an important ball-point to compare the price of crude oil to that of natural gas. In the example given, natural gas trades at a 7-8 times discount to crude oil. Historically natural gas has traded at a significant discount to oil, but at the beginning of 2009 for instance it traded more on a parity, or close parity with oil. By August 2009 the price of natural gas had tumbled so much that oil cost 26 more than gas, the biggest gap since January 1992. Oil cost 8.4 times more than gas on average during the decade between 1999 and 2009.

Oil and gas prices have never moved in a lock step, one of the main reasons being that the former is part of a global market whilst natural gas is traded via pipeline on more localized markets. Tankers can move oil or refined products to anywhere from anywhere, and will do so if prices rise in one region relative to those in another. Growing demand for oil in Asia, as well as fears of instability in the Middle East have helped to raise oil prices. Although the market for LNG is growing, natural gas, has still limited worldwide transportation capacity.

Natural gas and crude oil prices have had a stable long-run relationship despite periods
when a large exogenous spike in either crude oil or natural gas prices may have produced
the appearance that these two prices had decoupled.