At a news conference Tuesday morning, CALPIRG unveiled the report, which found the average gas price in May of $3.96 a gallon would have been just $3.13 if it were not for Wall Street speculators.
"The report found that large scale speculative trading in the oil futures market means that U.S. consumers paid on average 83 cents more per gallon in May due to Wall Street speculation," CALPIRG spokesperson John Fox said.
The report from the Political Economy Research Institute figured that's a $41 a month premium for every car on the road.
But the head of UC Berkeley's Energy Institute says that's just not true.
"This is diagnosis by exclusion; 'We can't think of any other reason prices are so high, so we're going to say it's speculation,'" Prof. Severin Borenstein, Ph.D., said.
Borenstein says in fact, the economics of the oil market are much more complex and there are real reasons for the current rise in prices.
"Saudi Arabia has a lot of extra oil that it is choosing not to produce. Likewise, the cutback in Libya's production has a significant impact on the market," Borenstein said.
Borenstein says those cutbacks in the face of rising demand are much more significant than Wall Street's side bets on what the price of oil will be in the future.
"There's really just no evidence in the serious economic analysis that speculators are a significant cause of high oil prices," he said.
One of the co-authors of the report, an economist at the University of Massachusetts, says the evidence is that prices simply went up for the first quarter of 2011 at a time when supply actually outstripped demand. This disagreement between economists is just part of what the Commodities Futures Trading Commission is looking at right now as they seek to put limits on the trading of oil futures.