If you start with 1998-1999 as a baseline for oil prices and assume a natural growth rate of 17.68%, you track oil prices pretty closely through mid-2004. Iraq in March 2003 isn't even a blip on the chart, even when the wackos start blowing up pipelines. From mid-2004 until late 2006, oil is going up at more like 40% a year - unsustainable, a spec bubble. Maybe Katrina in 2005 had something to do with it, but oil prices started zooming a year before. It's "excess liquidity", going around from one market to another looking for something to do with itself and blowing up one bubble after another. Project the 17.68% line through to this year, and you get a range of $47-73. with a median of $60.60, which is roughly where we are. In other words, we're back to sanity, more or less. If there's a recession, oil is likely to undershoot that $47 price - hence $40 oil.
Actually, a 17.68% growth rate looks high to me. World GDP is growing at 5%, add 2-3% for inflation, another 5% say for diminishing marginal returns in production Subtract for diminishing energy density (advanced economies consume less energy per unit of GDP than emergin ones, so that demand for oil should increase more slowly than GDP as more and more countries cross the threshold and become "advanced" ... I don't know how to account for 17.68%, except it's what fits the curve, but I certainly can't account for 40%.