With the US economy stuck in the doldrums, weakening the demand for oil and its products, and with the fall of at least portions of Tripoli foreshadowing the eventual return of Libyan oil exports to the market, it must seem puzzling that US gasoline prices haven't dropped farther in the last few weeks. As of Monday, the national average price for unleaded regular stood at $3.58 per gallon, only 3% lower than a month ago, when crude oil was just shy of $100 per barrel, compared to around $84 today. On Monday's evening news, CBS ran a segment attempting to explain this apparent disconnect. Unfortunately, they over-simplified the main explanation with a graphic showing cheaper domestic crude oil mixing with higher-priced imported oil. The "A" answer to this question is simpler but not well-understood, even though its elements have been fairly widely reported: Americans are simply looking at the wrong crude oil price, out of long habit. When you compare current gasoline prices and more representative crude oil prices, there isn't much of a disconnect about which to grumble.

The source of this confusion is the price of West Texas Intermediate crude oil (WTI), which for three decades has been the most watched and widely traded oil price in the world, and the basis of what most people mean when they talk about the price of "oil." In fact, there are numerous distinct grades of oil, each with its own price reflecting quality, location and availability. However, until recently most of these prices were based on the price of WTI, plus or minus a relatively narrow band of premiums or discounts, so using WTI as a barometer of all oil prices didn't cause much confusion or inaccuracy. The emergence of a pronounced and lengthy supply bottleneck at the Cushing, OK delivery location for the WTI futures contract has exploded this convenient set of relationships and assumptions.

Because more oil has been going into tankage at Cushing than was leaving those tanks over the last year or so, the price of WTI--itself a category, rather than a single stream of oil--has become massively depressed relative other types of crude oil, not just imported oil but also oil in other locations in the US that aren't affected by the bottleneck. Consider some important examples. While oil produced in Kansas, New Mexico and Oklahoma is all cheaper due to the Cushing effect, Louisiana Light Sweet, which historically traded within a dollar of WTI, is now worth nearly $20/bbl more, putting it much closer to the price of UK Brent crude--the best current gauge of global oil prices--than to WTI. Meanwhile, Bloomberg reports Alaskan North Slope crude (ANS) for delivery on the West Coast at nearly $107/bbl, or $24 over WTI. That's surprising, considering that ANS is heavier and higher in sulfur than WTI, and thus requires more processing. Just as remarkably, California heavy crude at Midway-Sunset is quoted at more than $10/bbl above WTI, when based on history and quality I would expect to see a discount of at least that magnitude. In other words, for now at least, the price of WTI is simply no longer representative of the crude that many US refineries are processing, from either foreign or domestic sources.

When you compare the wholesale price of gasoline from US refineries near the East, West and Gulf coasts to the cost of their crude inputs at around $100 or more, the difference of $15-17/bbl isn't historically unusual. Meanwhile, refineries in the middle of the country have recently been experiencing much stronger margins. This disparity is evident in the second quarter earnings reported by various US refining companies. East coast refiner Sunoco, which hasn't benefited much from cheap WTI, reported a net loss for the quarter, while Valero, with a bigger and more geographically dispersed refining system that includes facilities processing large quantities of WTI-related crude, saw refining segment earnings increase by 39% compared to the second quarter of 2010. The Cushing effect was even more pronounced for the recently merged HollyFrontier Corp., which apparently runs little crude that isn't priced near WTI and saw second-quarter net income almost triple versus 2Q2010. Even after that extra profit margin, gas prices in Tulsa, OK are currently as low as $3.30/gal., or about 15 cents per gallon less than the national average after adjusting for differences in state gas taxes.

Gasoline prices are determined by more than just crude oil prices, though in the long run the two must move together, because the latter represents the largest component of the cost of the former. At least until the bottleneck in Cushing is resolved by new pipeline capacity to the Gulf Coast, one option for which was just canceled, we will need to look beyond our old reliable WTI price indicator in order to compare gasoline and crude prices on a representative basis. I've been paying a lot more attention to the Brent market, and the Wall St. Journal still publishes daily prices for Louisiana Light Sweet and ANS. When and if those indices drop significantly, then it will be time to start looking for a commensurate drop in retail gasoline prices at the pump.