SAN FRANCISCO (KPIX) — Lawmakers and drivers alike are calling on the state Attorney General to investigate the cause of California’s gas prices. Most drivers expect to pay more, but a recent report by the state’s Petroleum Market Advisory Committee says they pay as much as thirty cents more per gallon than they should and economists can’t explain why.

Up until 2015, economists said they could explain why the price at the pump is so much higher in California than other states: taxes, a special environmental blend of gasoline, cap-in-trade.

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But in the last three years, economist Severin Borenstein says, prices at the pump exceed even the demands of those things and he doesn’t know why.

“If you look from 2000 to 2014,” Borenstein tells KPIX. “The average differential was just a couple pennies, an in no year was it more than ten or 12 cents. In 2015 it skyrocketed.”

Borenstein discovered what he calls the ‘gas surcharge’ while on the Petroleum Market Advisory committee. They were tasked with studying why gas prices are so high. He says the mysterious extra costs come to about 20 to 30 extra cents per gallon, which, over the last three years adds up to $17 billion dollars drivers have paid for what seems like, he says, no reason.

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“That’s not fair, says driver Alice Byer. “It’s not fair to the economy, to us, the striving people just trying to maintain and balance, just to keep your neck above water.”

It’s not just drivers that are upset. Lawmakers are, too.

Assemblyman Marc Levine and 18 other lawmakers have asked the state Attorney General to investigate in an effort to find out why and how this is happening.

“We understand everyone makes a profit,” Levine says, “but they cannot take advantage of a non-competitive marketplace to get over on consumers and we need to put an end to that.”

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The Attorney General has not yet said whether he will investigate.