Data shows average monthly retail fuel prices in the United States from 2000 to 2017. The price of petroleum fuels (gasoline and diesel fuel) is the primary driver of liquid fuel prices. This is because the liquid fuels are used in non-dedicated vehicles and can be substituted out by petroleum fuels if their price rises too high, therefore decreasing demand until the price drops to close that of the petroleum fuel. However, natural gas and electricity prices have been buffered from this driver because transportation only constitutes a tiny portion of their markets. LNG was first tracked in July 2016.