This year, scary clowns, scary dolls and scary suburbanites have drawn audiences to the movies in droves. Even with two months remaining, 2017 has already become the biggest box office year ever for horror. Scary movies have collected $733 million in ticket sales, according to the website Box Office Mojo. The runaway success of “It” (more than $300 million and counting) and “Get Out” ($175 million) led the way, but October is a golden month for horror and will surely add more to that tally. “Happy Death Day” was No. 1 when it opened this month (on Friday the 13th), and a new entry in the hit “Saw” franchise, “Jigsaw” (due Oct. 27), should also raise the total.

How has horror fared at the box office in previous decades? Going back to the 1970s, I used data from Box Office Mojo to track the genre’s rise as a moneymaking force, focusing on one key year from each decade. Box Office Mojo breaks horror down into 10 subcategories on its site and its editor, Brad Brevet, has struggled with the question of what constitutes a horror movie. He tried to bring some clarity with a new list. “When ‘It’ came out I created an R-rated horror list on Mojo,” he wrote in an email. “That, at least, felt representative of the horror genre.”

We used the R-rated list as a reference point, but the highest-grossing year for each decade is based on figures collected from all the films the site considers horror. Also, these numbers have not been adjusted for inflation (which would turn “The Exorcist” into a $983 million earner).