This is, when you think about it, a potentially disturbing piece of information. The whole premise behind sales, or supermarket specials, is that we, as consumers, are very aware of the prices of things and will react accordingly: we buy more in response to lower prices and less in response to higher prices. But if we'll buy more of something even if the price hasn't been lowered, then what's to stop supermarkets from never lowering their prices? What's to stop them from cheating us with meaningless "everyday low price" signs every time we walk in? The answer is that although most of us don't look at prices, every retailer knows that a very small number of people do, and if they find something amiss — a promotion that's not really a promotion — they'll do something about it. If a store tried to pull the sales stunt too often, these are the people who would figure it out and complain to management and tell their friends and acquaintances to avoid the store. These are the people who keep the marketplace honest. In the ten years or so since this group was first identified, economists have gone to great lengths to understand them. They have found them in every walk of life and in every socioeconomic group. One name for them is "price vigilantes." The other, more common, name for them is "Market Mavens."

Linda Price, a marketing professor at the University of Nebraska and a pioneer in Maven research, has made videotapes of interviews she's done with a number of Mavens. In one, a very well dressed man talks with great animation about how he goes about shopping. Here is the segment, in full:

Because I follow the financial pages closely, I start to see trends. A classic example is with coffee. When the first coffee crunch came ten years ago, I had been following the thing about Brazilian frost and what it would do to the long-term price of coffee, and so I said I'm going to stockpile coffee.

At this point in the interview, an enormous smile breaks across the man's face.

I ended up with probably somewhere between thirty-five and forty cans of coffee. And I got them at these ridiculous prices, when the three-pound cans were $2.79 and $2.89… Today it's about $6 for a three-pound can. I had fun doing that.

Do you see the level of obsession here? He can remember prices, to the cents, of cans of coffee he bought ten years ago.

The critical thing about Mavens, though, is that they aren't passive collectors of information. It isn't just that they are obsessed with how to get the best deal on a can of coffee. What sets them apart is that once they figure out how to get that deal, they want to tell you about it too. "A Maven is a person who has information on a lot of different products or prices or places. This person likes to initiate discussions with consumers and respond to requests," Price says. "They like to be helpers in the marketplace. They distribute coupons. They take you shopping. They go shopping for you…They distribute about (our times as many coupons as other people. This is the person who connects people to the marketplace and has the inside scoop on the marketplace. They know where the bathroom is in retail stores. That's the kind of knowledge they have." They are more than experts. An expert, says Price, will "talk about, say, cars because they love cars. But they don't talk about cars because they love you, and want to help you with your decision. The Market Maven will. They are more socially motivated."

Price says that well over half of Americans know a Maven or someone close to the Maven's description. She herself, in fact, based the concept around someone she met when she was in graduate school, a man so memorable that his personality serves as the basis for what is now an entire field of research in the marketing world.

"I was doing my Ph.D. at the University of Texas," Price said. "At the time I didn't realize it, but I met the perfect Maven. He's Jewish and it was Easter and I was looking for a ham and I asked him. And he said, well, you know I am Jewish, but here's the deli you should go to and here's the price you should pay." Price started laughing at the memory. "You should look him up. His name is Mark Alpert."

Mark Alpert is a slender, energetic man in his fifties. He has dark hair and a prominent nose and two small, burning, intelligent eyes. He talks quickly and precisely and with absolute authority. He's the kind of person who doesn't say that it was hot yesterday. He would say that we had a high of 87 degrees yesterday. He doesn't walk up stairs. He runs up them, like a small boy. He gives the sense that he is interested in and curious about everything, that, even at his age, if you gave him a children's chemistry set he would happily sit down right then and there and create some strange new concoction.

Alpert grew up in the Midwest, the son of a man who ran the first discount store in northern Minnesota. He got his doctorate from the University of Southern California and now teaches at the University Of Texas School Of Business Administration. But there is really no connection between his status as an economist and his Mavenism. Were Alpert a plumber, he would be just as exacting and thorough and knowledgeable about the ways of the marketplace.

We met over lunch at a restaurant on the lakefront in Austin. I got there first and chose a table. He got there second and persuaded me to move to another table, which he said was better. It was. I asked him about how he buys whatever he buys, and he began to talk. He explained why he has cable TV, as opposed to a dish. He gave me the inside scoop on Leonard Maltin's new movie guide. He gave me the name of a contact at the Park Central Hotel in Manhattan who is very helpful in getting a great deal. ("Malcolm, the hotel is ninety-nine dollars. And the rack rate is a hundred and eighty-nine dollars!") He explained what a rack rate is. (The initial, but soft, retail asking price for a hotel room.) He pointed at my tape recorder. "I think your tape is finished," he said. It was. He explained why I should not buy an Audi. ("They're Germans, so it's a pain dealing with them. For a while they would give you an under-the-counter warranty, but they don't anymore. The dealer network is small, so it's hard to get service. I love driving them. I don't like owning them." What I should drive, he told me, is a Mercury Mystique because they drive like a much more expensive European sedan. "They aren't selling well, so you can get a good deal. You go to a fleet buyer. You go in on the twenty-fifth of the month. You know this… ") Then he launched into an impossibly long, sometimes hilarious, description of the several months he took to buy a new TV. If you or I had gone through the same experience — which involved sending televisions back, and laborious comparison of the tiniest electronic details and warranty fine print — I suspect we would have found it hellish. Alpert, apparently, found it exhilarating. Mavens, according to Price, are the kinds of people who are avid readers of Consumer Reports. Alpert is the kind of Maven who writes to Consumer Reports to correct them. "One time they said that the Audi 4000 was based on the Volkswagen Dasher. This was the late 1970s. But the Audi 4000 is a bigger car. I wrote them a letter. Then there was the Audi 5000 fiasco. Consumer Reports put them on their list of thou shaft not buy because of this sudden acceleration problem. But I read up on the problem in the literature and came to believe it was bogus… So I wrote them and I said, you really ought to look into this. I gave them some information to consider. But I didn't hear back from them. It annoyed the hell out of me. They are supposed to be beyond that." He shook his head in disgust. He had out-Mavened the Maven bible.