Available Crude Capacity Affects Price
Source: Reuters WTI April 1999-Aug 2004; EIA Calculations
SThis chart shows the relationship between crude oil prices and surplus production capacity since 1999, or about the time we saw the shift in prices up to around $30 per barrel.

SNotice that price rises almost $10/barrel as surplus capacity drops from about 2 MMB/D to where we are today at about 0.5 MMB/D.