It has been a remarkable year for public demonstrations. More than 1 million people filled Parisian streets on Sunday, a show of unity after last week’s terror attacks in France. In August, protests erupted in Ferguson, Missouri, after an unarmed black teenager, Michael Brown, was fatally shot by a police officer.

And in New York in September, tens of thousands turned out for the People’s Climate March, one of the largest environmental marches in history. Dana R. Fisher, a sociologist, was there seeking answers to basic questions: Why do individual citizens engage in the democratic process, and how do protests come together?

Fisher is the subject of “Political Action,” directed by Jamie Schutz. It’s the second film in “The Collectors,” a series of 10 short documentaries from FiveThirtyEight and ESPN Films about the passionate people who collect data.