For generations, introductory courses in economics and business have taught eager students that the fundamental objective in business is relatively simple: Identify a need in the marketplace, and then develop the product or service to supply that need.

Generally, this system works well. Smart entrepreneurs can quickly divine the need for a particular product at a particular time. The simplest example is the weather. No sooner do rain clouds gather in New York City than cadres of street vendors appear on the streets armed with cheap umbrellas. (So what if they are essentially disposable and practically fall apart upon their first use? For $3, you can save yourself from getting drenched.)

But when the weather doesn’t flash signals about what products are needed, businesspeople have to rely on signals from the marketplace.

With gas prices high and SUVs languishing on dealer lots, car companies have figured that this might be a good time to roll out more fuel-efficient models. In the entertainment world, once a phenomenon emerges — a reality show, a book about the woes of being single in New York — copycats quickly follow. Which is how American Idol begat America’s Got Talent, and how The Bachelor begat The Bachelorette.

The underlying assumption of all this activity is that consumers — not engineers or investors, not CEOs or salespeople — know exactly what they want. Indeed, companies don’t just sit around and wait until it rains to roll out umbrellas. They’re engaged in a constant process of trying to figure out what their customers will spend money on. In general, today’s large corporations tend to rely less on instinct and more on data. They convene focus groups, commission polls, and dispatch anthropologists to watch people cook dinner at home. They also crunch data obsessively.

But listening to what consumers say can sometimes lead companies astray, especially when they listen to small groups of consumers. Based on some consumer-generated information, Coca-Cola concluded in the 1980s that the enduring formula for the nation’s most popular soft drink needed to be scrapped. Oops! New Coke, which was developed with the intent of giving consumers of sweet sodas exactly what they said they wanted, has gone down as one of the great brand debacles of all time.

In July, the Wall Street Journal reported that KitKat, the venerable British candy bar, had similarly gone astray by tinkering with the basic formula. Eager to boost sales, a new executive decided that it would make sense to roll out all sorts of newfangled flavors. Consumers seemed to want it: small tests of versions like a lemon yogurt KitKat in Germany had done well. And so the variations came fast and furious. Strawberries and cream, tiramisu, red berry, a low-carb version. Broadly speaking, the variations were met with a stiff British upper lip. Worse, annoyed munchers took out their aggression on the core brand. Sales of all KitKat products fell sharply in Britain.

The challenge for marketers is to figure out if the product innovations that are well-received in focus groups will actually catch on in the marketplace. At automobile manufacturers, which are constantly taking the pulse of their consumers, engineers respond to perceived consumer demand by continually offering more bells and whistles. After all, who would say no, in theory, to a seat that can move in ten different ways, or that comes with climate controls similar to those found in an operating room? Or to a sound system sophisticated enough to power an edgy night club? But the end result is that for many drivers, today’s options-packed vehicles are simply too difficult and confusing to operate.

Now, this may be heretical to suggest, but it’s possible that the customer isn’t always right, that the consumer does not know best. And indeed, this counterintuitive insight can represent the greatest opportunity for inventors, entrepreneurs, and executives. Filling existing needs is an inherently reactive business. But when you can bring to market something that people don’t even know they want, you can create — and dominate — an entirely new market.

Consumers generally want improved versions of products or services they already know, not a fundamentally different version of something they already know. At the turn of the 20th century, people were content with the railroads and the horse and carriage. Henry Ford used to say that if he had given customers what they wanted, he would have invented a faster horse. Instead, he invented the automobile. The newfangled invention took some getting used to, but it caught on, and Ford put the nation on wheels.

Or dial back to the phone business in the 1980s. People said they wanted incremental improvements to the household item. So the big phone companies developed touch-tone phones instead of the old-fashioned rotary dials, and cordless phones and call waiting instead of that annoying busy signal.

Chatters were generally happy and satisfied. There were no groups of disgruntled folks picketing in front of AT&T;’s headquarters, demanding tiny wireless phones that would enable people to chat idly as they sat in their cars, in baseball stadiums, or in restaurants. And yet when entrepreneurial companies rolled out cheap, functional cell phones in the 1990s, they became something akin to a utility.

The list of things that went from being completely off the radar screen to staples of modern life is long: shopping malls, amusement parks, all manner of ethnic food. If marketers had convened a series of focus groups 20 years ago and asked what people thought about eating raw fish rolled up in seaweed, the response would have been a resounding “No!” And yet today, sushi restaurants are a staple of strip malls all over the country, and spicy salmon rolls can be found near the deli counter in virtually every supermarket.

Or how about the iPod? Let’s say one of those consumer-oriented anthropologists came to your house ten years ago, and asked: “Do you need to carry your entire music collection around with you in digital format?” The answer would surely have been no. We were doing just fine with our radios and Walkmen. So the established players gave us modified versions of the existing technology: smaller radios and Discmen. It took an outsider to the music industry — Apple — to come up with the revolutionary iPod. Today, of course, it seems that people simply can’t leave the house without taking their entire collection of Beethoven symphonies and Britney Spears singles (this is a purely hypothetical mix, you understand). Indeed, so many people are tethered to their iPods that an alien landing on Earth today might think that they’re a device that provides some sort of essential nutrition.

One of the songs on my iPod is Joni Mitchell’s “Big Yellow Taxi.” One line goes: “Don’t it always seem to go, that you don’t know what you’ve got till it’s gone.” True. But there’s also an economically powerful corollary: A lot of the time, you don’t know what you’re missing until you get it.