Game of Thrones kills off almost as many characters each season as it introduces. The most iconic scenes, like The Red Wedding, are ones in which the show mercilessly kills off beloved characters quickly and without warning. Fans love to guess who will die next, and some of those fans are mathematicians who have written analytical papers that begin with spoiler warnings.
The HBO show is based on the Song of Ice and Fire books by George R.R. Martin. As the series is a fairly faithful adaptation, fans of the show often look to the books for clues about what will happen in the upcoming season. Richard Vale, a statistician at the University of Canterbury in Christchurch, used Bayesian statistics (a field of mathematics concerned with predicting future events) to analyze the Song of Ice and Fire books and find out who will die next.
Each chapter of the books is told from the point-of-view of a character. Vale's method looks at those chapters to determine how long a character will stick around.
"Presumably, dead implies zero POV chapters," Vale told Wired. "So there should be a small amount of information about the potential deaths of characters if we believe the model."
According to Vale's data there's a 38 percent chance that Jon Snow will have no chapters in the next book, but a 67 percent chance in the sixth book, meaning that Jon Snow may be dead by the end of the sixth book. Like all predictions, though, Vale's are fallible. "The model can only say that, based on the number of POV chapters observed so far, [Jon Snow] has about as much chance of survival as the other major characters."
Because the model is based on straight mathematics, it does not allow for common sense conclusions, so Vale's model is best used in relation to the knowledge readers already have. Some characters who are minor may go the whole series alive and never have a point-of-view chapter. It's the major characters we need to pay attention to.