If you’re uncertain why companies like ESPN and Activision have been making big acquisitions and investments in esports, here’s a good answer: because more than 100 million viewers spend lots of time — really, lots of time — watching competitive gaming.

More than 800 million hours over the past 10 months.

Market research firm Newzoo said that people watched 803.7 million hours of esports from August to May. It also reported that competitive gaming provided 14 percent to 31 percent of what folks were watching overall on Twitch. It also found that event and league organizers got the biggest slice of this viewership, 71.3 percent — with Riot, which runs all events for its dominant League of Legends multiplayer online strategy game, and leading organization ESL putting on half of these hours.

Newzoo gathered this data from the public Twitch API. None of these hours include events that weren’t broadcast on Twitch, such as viewership for the TBS network’s Eleague series.

The other 3.2 billion hours watched on Twitch between August 2015 and May 2016 consisted of consumer streams as well as streams from pro-players.

Three big events helped make October the top month for esports on Twitch: the League of Legends World Championship and the ESL’s One New York and the MLG’s World Finals, both for Dota 2, another multiplayer online strategy game. August came in second, again thanks to three events: the summer playoffs for League of Legends, the final of The International 5 for Dota 2, and ESL One Cologne, a Counter-Strike: Global Offensive event (that’s a first-person online shooter, breaking League’s and Dota’s run here).

December, of course, was the slowest month for esports, as leagues tend to hold fewer events during the holiday month, with 49.7 million hours watched (13.8 percent of Twitch’s total).

The PC Gaming channel is presented by Intel®'s Game Dev program.