This study argues that movies with 2 more more black actors in main roles boost film revenues by more than 60%. Unfortunately, in 85% of movies there are neither no or just one black actor in a major role, and these are the films that made less. It is unclear what other factors are controlled for (are all the movies with multiple black actors big budget superhero movies?), nor whether the authors looked at worldwide revenues or domestic. The argument made by studios is that black actors do poorly in China, which is the reason why John Boyega’s image is minimized in the Star Wars posted made for China.
For their study, Kuppuswamy and Younkin took a look at 723 mainstream English-language movies released in major theaters between 2011 and 2015, and determined the number of black actors in lead roles in each film. In nearly two-thirds of the films, there were no black actors cast in any lead roles. In 23 percent of the films, there was one. Only in 11 percent were there two or more black principals.
The relative rarity of diverse casts might suggest that they have little money-making potential, but after parsing the data, the researchers came to the conclusion that audiences don’t reject films with diverse lead actors—they actually prefer them. According to Kuppuswamy and Younkin, adding more black actors in principal roles had a beneficial effect on box-office outcomes. The films that had only one black lead actor performed about as well as those films that had none. But films that had two or more black actors playing main roles performed even better, boosting box-office revenues by more than 60 percent compared to films that didn’t have any black lead actors. [link]
Here is the original study on SSRN: “Blaming the Customer: The Effect of Cast Racial Diversity on the Performance of Hollywood Films”