Drivers who have long suspected that gasoline prices rise much more quickly in response to increases in world oil prices than they fall when the price of crude oil drops are correct -- they do. But the culprit behind the discrepancy is not the giant oil companies, as many people might believe, but the retail market, according to the results of a study conducted by researchers at UC Davis and UC Berkeley. Headed by Severin Borenstein, an associate professor of economics at UC Davis, the research team analyzed price information available on the market transactions that occurred in the production and distribution of gasoline from January 1986 to December 1990. They found that retail gasoline prices do adjust more quickly to increases rather than decreases in the price of crude oil, but wholesale prices do not. Over a 10-week period, a five-cent-per-gallon increase in the price of crude oil would cost average consumers about one dollar more than they would save if there had been a five-percent drop in the price of crude. One possible explanation for this "asymmetry" in pricing is that, when crude oil prices fall, stations might choose to maintain their old prices until another station lowers its prices, forcing others to go along. It's also possible, Borenstein says, that during periods of volatile changes in the price of gasoline, consumers are less likely to shop around for the best deal, giving stations an incentive to keep prices up even after wholesale prices drop.