How do they predict the weekend box office before Sunday's numbers are in?

To estimate Sunday's take at the box office, it's all about the drop. Saturday is typically a bigger day at the movies than Sunday, so numbers naturally decline from Saturday to Sunday. Knowing the size of this change makes it fairly easy to predict how well a certain movie will do on Sunday, often before the first moviegoers settle in a seat at their local theater for the day's first matinee.

In general, ticket sales for any given movie decline between 25 percent and 30 percent from Saturday to Sunday [source: Mondello]. As an example, consider the percentage drop for the top 10 movies on the weekend of Aug. 15 through Aug. 17, 2014. The Saturday to Sunday drop in ticket sales for this period ranged from 23.3 to 37.4 percent, with an average drop of 28.7 percent [source: Box Office Mojo]. To estimate Sunday sales, simply multiply the numbers for Saturday by 65 to 75 percent. Add this figure to Friday and Saturday figures and you've got a weekend box office estimate.

Of course, predicting the weekend box office is anything but an exact science, and this 25 to 30 percent decrease doesn't always hold true. Variety estimates the weekend drop at a much wider 20 to 50 percent from even Friday to Saturday, though the studios and industry analysts can often estimate exactly where in that range that a given movie will fall based on factors such as demographics, genre, exit polls and release date [source: McClintock]. For example, a movie geared at teens will likely have a fairly large drop from Saturday to Sunday because teens tend to attend movies on Friday and Saturday nights. A G-rated film might have a smaller than usual drop thanks to Sunday daytime shows, which are popular with families [source: Mondello].

For an example of how studios use historical data and experience to pinpoint the potential drop and predict Sunday ticket sales, consider "Star Wars." Slate reported that "The Phantom Menance" had a Saturday-to-Sunday drop of 10 percent on its opening weekend, while "Attack of the Clones" came in at 22 percent. To predict the box office for "Star Wars," Fox assumed a drop of 16 percent based on the performance of the other films. Its guess was remarkably close and allowed it to accurately estimate the weekend box office for "Revenge of the Sith", which had a 15.9 percent drop from Saturday to Sunday [source: Snyder].

No matter how much analysis goes into predicting Sunday's box office take, some movies are destined to surprise both the studios and the public. Why? It's important to keep in mind that the studios are the ones predicting how a movie will do and what the expected Sunday drop will be. Media outlets simply report on predictions and estimates provided by the studios, which have strong motivation to either inflate or understate the box office. Some prefer to go bold and predict record-breaking ticket sales in an effort to drive interest in the film, even at the risk of coming up a little short. Others prefer more conservative estimates to avoid a disappointing showing when the numbers come in.

In addition to the obvious bias of having the studios predict their own ticket sales, plenty of other factors can make estimating Sunday sales unusually challenging. A major holiday falling on a traditionally busy or slow movie day or even a natural diasaster can throw a loop into the world of movie analytics. "Avatar" likely suffered from slow sales when a major winter storm blanketed the East Coast on its opening weekend in 2009, and box office predictions for "Zoolander" busted when the film came out just after the Sept. 11 terrorist attacks.

Of course, movies can overperform just as easily as they can bust. "Avatar" shocked everyone when it registered a sales drop of just 3.1 percent from Saturday to Sunday on its opening weekend in 2009 [source: Box Office Mojo]. The year before, Warner Brothers faced plenty of criticism when the studio predicted a $150 million weekend for "The Dark Knight." Thanks to a Sunday drop of just 8 percent, the movie shattered all sorts of records as it took in $158.4 million during a single weekend [source: Finke].

While studios and the media can use historical patterns to predict Sunday ticket sales before they happen, there's no way to know box office results for sure until the final numbers are in. Hey, that's Hollywood.