While crude oil prices have been cut roughly in half since June last year, retail prices for regular and premium gasoline have not fallen by nearly as much, with an average fall of 30 percent and 20 percent in the same period, respectively. Conversely, when crude prices rocketed from 2007 onward, retailers were quick to pass on the price changes.

Skeptical drivers might assume companies that operate down the fuel supply chain collude and manipulate prices to cash in large profits. In fact, in the past 30 years numerous congressional hearings and government reports have studied the apparent asymmetries between wholesale and retail prices for fuel and natural gas — but without any clear conclusion.

Economists call this behavior of prices "rockets and feathers," a term originally coined by R.W. Bacon in 1991 to describe the phenomenon of firms responding with a greater speed to cost increases than decreases.

Empirically, the phenomenon has been proven across the globe. The Boston Consulting Group (BCG) has identified the rockets and feathers phenomenon in retail gasoline markets in Canada, the U.S., Chile and numerous European countries. Moreover, according to research by economist Sam Peltzman, the phenomenon is not only restricted to the retail gasoline industry, but embraces two-thirds of all markets following a study of 242 diverse product markets.

Theoretically, however, the origins of these price asymmetries are hard to explain. A recent research paper published by the Economic Analysis Group of U.S. Department of Justice, finds that one explanation are so-called "consumer search costs," which occur when consumers are ill-informed about the cost structures of retailers.

The paper proves this by showing that prices for premium gasoline fall slower than prices for regular gasoline. The reason is that premium consumers who ignore advice by engineers and scientists that there is little need of premium, but still consume it, are badly informed.

According to Michael Noel, those search costs are exacerbated by the sensitivity of consumers with respect to a rise compared to a fall in fuel prices. Apparently, consumers care more about an increase in gas prices than a drop. A rise in fuel prices squeezes consumers' budgets, and motorists will search for the cheapest fuel station, while they are more callous once prices fall a bit and search less.

But, of course, this is not the full story. There are many other reasons for these price disparities, including the complexity of the downstream market.

The supply chain has many twists and turns, from wholesale crude oil markets to the final retailer. The cost of oil makes up only about half of the cost of a gallon of gasoline, according to the U.S. Energy Information Administration. The other major costs include refining costs and profits, distribution costs and retailers' profits, and state and federal tax.

On average, a gallon of regular gasoline in August cost $2.60. The cost of crude oil accounted for less than 50 percent, while refining contributed about 25 percent, distribution and marketing (including gas station profits) made up 13 percent and taxes 16 percent.

At the link between each of these price components, there is a leeway for the different actors involved to increase or reduce costs. A study from 1997 by BCG shows with price data from four distinct links of the gasoline supply chain crude oil, spot wholesale, local rack and retail that price asymmetries occur at every link except for the transmission from spot to local rack.

Since February, refineries have made the biggest gain in the U.S. The last time refining costs represented about 20 percent of gasoline prices was in June 2007, according to the EIA.

One thing is for sure, it's unlikely that retailers collude to rein in massive profits, otherwise new businesses would enter the market quickly. However, one could observe the opposite over the past years with a decline in the number of retail stations and exit from the retailing segment by large branded oil companies like ExxonMobile and Chevron, according to Michael Noel.

Whatever the reasons for these massive price disparities (incoherencies at the supply link with refineries or otherwise), transparency might be one of the best solutions. Providing consumers with a clear and timely overview of all of the key price components could be a step forward.