So does a listener’s own independent reaction to a song count for anything? In fact, intrinsic “quality,” which we measured in terms of a song’s popularity in the independent condition, did help to explain success in the social-influence condition. When we added up downloads across all eight social-influence worlds, “good” songs had higher market share, on average, than “bad” ones. But the impact of a listener’s own reactions is easily overwhelmed by his or her reactions to others. The song “Lockdown,” by 52metro, for example, ranked 26th out of 48 in quality; yet it was the No. 1 song in one social-influence world, and 40th in another. Overall, a song in the Top 5 in terms of quality had only a 50 percent chance of finishing in the Top 5 of success.

In our artificial market, therefore, social influence played as large a role in determining the market share of successful songs as differences in quality. It’s a simple result to state, but it has a surprisingly deep consequence. Because the long-run success of a song depends so sensitively on the decisions of a few early-arriving individuals, whose choices are subsequently amplified and eventually locked in by the cumulative-advantage process, and because the particular individuals who play this important role are chosen randomly and may make different decisions from one moment to the next, the resulting unpredictability is inherent to the nature of the market. It cannot be eliminated either by accumulating more information — about people or songs — or by developing fancier prediction algorithms, any more than you can repeatedly roll sixes no matter how carefully you try to throw the die.

This, obviously, presents challenges for producers and publishers — but it also has a more general significance for our understanding of how cultural markets work. Even if you think most people are tasteless or ignorant, it’s natural to believe that successful songs, movies, books and artists are somehow “better,” at least in the democratic sense of a competitive market, than their unsuccessful counterparts, that Norah Jones and Madonna deserve to be as successful as they are if only because “that’s what the market wanted.” What our results suggest, however, is that because what people like depends on what they think other people like, what the market “wants” at any point in time can depend very sensitively on its own history: there is no sense in which it simply “reveals” what people wanted all along. In such a world, in fact, the question “Why did X succeed?” may not have any better answer than the one given by the publisher of Lynne Truss’s surprise best seller, “Eats, Shoots & Leaves,” who, when asked to explain its success, replied that “it sold well because lots of people bought it.”

This lesson is not limited to cultural products either. Economists like Brian Arthur and Paul David have long argued that similar mechanisms affect the competition between technologies (like operating systems or fax machines) that display what are called “network effects,” meaning that the attractiveness of a technology increases with the number of people using it. But even in markets that don’t exhibit obvious network effects (like markets for low-carb or organically produced food, fuel-efficient vehicles or alternative energy technologies), sudden shifts in consumer demand can still arise, persist and then shift again. These shifts often come as surprises but are soon explained away as mere reflections of changing public sentiments. Yet while in some sense these markets do reflect what people want, that is true only of what they want right now. If markets not only reveal our preferences but also modify them, then the relation between what we want now and what we wanted before — or what we will want in the future — becomes deeply ambiguous.

Our desire to believe in an orderly universe leads us to interpret the uncertainty we feel about the future as nothing but a consequence of our current state of ignorance, to be dispelled by greater knowledge or better analysis. But even a modest amount of randomness can play havoc with our intuitions. Because it is always possible, after the fact, to come up with a story about why things worked out the way they did — that the first “Harry Potter” really was a brilliant book, even if the eight publishers who rejected it didn’t know that at the time — our belief in determinism is rarely shaken, no matter how often we are surprised. But just because we now know that something happened doesn’t imply that we could have known it was going to happen at the time, even in principle, because at the time, it wasn’t necessarily going to happen at all.

That doesn’t mean we should stop trying to anticipate the future, any more than we should stop trying to make sense of the past. But it does mean that we should treat both the predictions and the explanations we are served — whether about the next hit single, the next great company or even the next war — with the skepticism they deserve.