Available Crude Capacity Affects Price
Source: Bloomberg  WTI Spot April 1999-Jan 2005; 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 about  $10/barrel as surplus capacity drops from about 2 million barrels per day to where we were during much of the second half of 2004 at about 0.5 million barrels per day.