Crude Oil is a naturally occurring liquid fossil fuel resulting from plants and animals buried underground and exposed to extreme heat and pressure. Crude oil is one of the most demanded commodities and prices have significantly increased in recent times. Two major benchmarks for pricing crude oil are the United States' WTI (West Texas Intermediate) and United Kingdom's Brent. The differences between WTI and Brent include not only price but oil type as well, with WTI producing crude oil with a different density and sulfur content. The demand for crude oil is dependent on global economic conditions as well as market speculation. Crude oil prices are commonly measured in USD. Although there have been discussions of replacing the USD with another trade currency for crude oil, no definitive actions have been taken.