They decline significantly from one year to the next because each barrel of oil taken from a reservoir reduces the pressure within the field, leaving less force available to push the next barrel of oil up the well.
Another reason to like Cracker Barrel is the presence of an activist investor helping to keep pressure on the company to improve performance: Sardar Biglari, the 35-year old Iranian-American manager of the Lion Fund and CEO of publicly traded Biglari Holdings (BH).
Members of Opec, made up of the world's major oil producers, have come under pressure to do something to stop the recent sharp rises in the cost of a barrel.