It certainly helps to be first on a weekend, but not all weekends are equally valuable. There are holiday weekends that can produce as much as 10 times the revenue as those in the slack season (when teenagers return to school). A Fourth of July second- or third-place movie can take in far more than a first-place finisher in October, since the total pie is so much larger. And films that open in the summer, no matter where they finish, will also earn more than fall films from Christmas DVD sales—due to the usual four-to-five-month embargo on the release of movies on DVD, summer films become fresh product on the market at holiday time.

Even in the era of global marketing campaigns, the US box office does not necessarily affect foreign revenues, which now are more important than the domestic take. For major movies, such as Avatar, more than 70 percent of the theatrical revenue is now earned overseas.

Nor does the box-office race provide an accurate measure of popular taste, since it lumps together movies that open on thousands of screens with those that choose to open on a few dozen screens, hoping to build gradually, benefitting from good reviews and strong word-of-mouth. Take, for example, Moonrise Kingdom, which opened on May 25, 2012, in only four theaters in two cities, and finished in 15th place, while Men in Black 3, which was first, was booked on 4,248 screens. Indeed, when studio marketing departments want to know the actual audience appeal of a movie, they track the per-screen average, the drop-off between Friday night (when there is no word-of-mouth) and Sunday, and the percentage drop after the first and second week. MIB3 was all but dead after three weeks, while Moonrise Kingdom moved to 924 theaters, and was still drawing audiences in late September, the 19th week of its run.

What a box-office victory actually measures is the breadth of the opening and the efficacy of the studio’s marketing arm: In other words, based on a barrage of 30-second TV commercials containing snippets of the film, which most moviegoers will have seen an average of seven times that week, how many people will show up on Friday night? This is a job the studios do amazingly well, but it has little to say about the intrinsic appeal of the movie.

To be sure, the race produces bragging rights every week for the winning studio’s marketing department, which then exploits the “No. 1” title in newspaper ads (for which studios spend, on average, about $4 million per title). And of course the publicity derived from this game further enhances the studios’ revenue.

But why does the media play along in the promotion? Generally, it is the only “news” available in the entertainment news cycle surrounding the opening. Any real digging into the economics of a movie takes considerable time, since the studios tightly seal all relevant information, such as the terms of distribution deals, financing, subsidies, and stars’ compensation, through Non-Disclosure Agreements. Even extras at times must sign NDAs (as I found out when I was an extra in Wall Street: Money Never Sleeps). By the time the economic picture becomes clear, if indeed it ever does, the news value of the project has faded.

Edward Jay Epstein is the author of The Hollywood Economist and The Big Picture: The Logic of Money and Power in Hollywood.