With gasoline prices now only medium outrageous, Gentle Reader may have forgotten how eager politicians were last year to find someone to blame when the pain at the pumps was off the charts.

The usual congressional investigation was hastily called, the usual outrage expressed, and the usual suspicions voiced with the usual lack of any economic effect. Then the political ritual was concluded, prices fell in the normal course of economic events, and few now ask whether there was anything to all that talk. It's a question worth asking as a lesson in politics - and economics.

Mark Pryor, the junior senator from Arkansas, was one of those making roundhouse accusations back then. In search of the nearest scapegoat for high oil prices, he settled for the same old one: dastardly Big Oil. The senator was out to protect us, so he said, from "the greed and profiteering in the oil marketplace" - not to mention economic literacy.

So what happened? Even though Sen. Pryor joined a number of his colleagues in trying to bully the Federal Trade Commission into cooking up some evidence to back up his conspiracy theory, all the FTC could do was reach the same conclusion it usually does: There was no substance to his charges.

Once again the bogeyman turns out to be nothing more sinister than the law of supply and demand. Sure enough, when supply dwindles and demand goes up,so do prices. Big surprise.

But every time gas prices go up, a certain kind of politician is shocked, shocked! Or at least pretends to be. And demands an investigation. Which is a lot easier than taking Economics 101 all over again.

Naturally the politician blames some vague, amorphous monster out there like Big Oil rather than the real-life owner-operator of your neighborhood filling station. After all, the little guy votes.

And it's too much trouble to think this thing through - as Henry Hazlitt did in his dandy little primer, "Economics in One Lesson."

To quote Mr. Hazlitt, "we cannot hold the price of any commodity below its market level without in time bringing about two consequences. The first is to increase the demand for that commodity. Because the commodity is cheaper, people are both tempted to buy, and can afford to buy, more of it. The second consequence is to reduce the supply of that commodity. Because people buy more, the accumulated supply is more quickly taken from the shelves of merchants. But in addition to this, production of that commodity is discouraged."

Gosh, just like gasoline last year.

If there's an avaricious cartel setting oil-and-gas prices, it's called OPEC. But oil sheikhs and Venezuelan caudillos are scarcely subject to a congressional investigating committee.

If there's a conspiracy at work here, it's the dismal science itself -economics. It's been refuting demagogues ever since they've been taking advantage of our anger, suspicion and ignorance. Hey, somebody's got to be blamed when we're unhappy. Especially somebody rich and powerful. What better scapegoat than Big Oil?

The art and science of economics may never be as simple or dramatic as Mark Pryor's populist rhetoric. But the study of economics may have the great advantage of clarifying things rather than hopelessly muddling them. Attached as we all may be to our own favorite conspiracy theory, along comes an actual investigation, and it goes poof. Which is just what's happened,again, to Mark Pryor's.

To quote the latest report from the FTC's investigators, whose prose isn't exactly scintillating: "The 2006 price increases were caused by a confluence of factors reflecting the normal operation of the market."

Aw shucks. And just when we were getting the tar and feathers ready for those oil executives.

And what were the factors that drove gas prices higher last summer? Among them, greater demand for fuel by vacationers (another big surprise), the still lingering effects of hurricanes (Katrina and Rita) that shut down refineries along the Gulf Coast, reduced oil refining capacity as producers switched to ethanol, and, as you might have expected, greater demand for both crude oil and ethanol. What, no conpiracy? How boring.

Once again the FTC found no evidence that gas prices were being manipulated by some sinister cabal in this country's boardrooms. Despite Senator Pryor's demand for more government regulation of gas prices (shades of Jimmy Carter's long lines back in the '70s), the FTC couldn't come up with any facts to support him.

This isn't the first time a sleek conspiracy theory has run aground on the rocky shore of fact. To quote Joseph Simons, a former director of the FTC's Bureau of Competition: "The FTC has looked at the same phenomenon, which occurs almost every year, year after year, and they get the same result. Why people think it's going to come out any different the next time is unclear. It's a waste of taxpayers' money."

But it's not a waste of ambitious politicians' efforts. They get to posture before the cameras and demand ACTION! -even if it's precisely the wrong kind.

The pols may be wrong again and again, year after year, but think of the advantages. They're able to strike while public anger is at its zenith, appease their louder and less thoughtful constituents, and they never have to say they're sorry by the time gas prices fall and the public's interest in the subject has waned. (Somehow they never get around to demanding a probe when gas prices go down.)

That's the way it is with wild accusations; the facts may never catch up. Or if they do, the story is relegated to the business section. Ho hum.

The price of gasoline may rise and fall and rise again, like that of any other commodity, but the market for demagoguery remains remarkably stable.