The rise of Twitch and the rise of esports can almost certainly be directly correlated, but what effect has esports had on the growth of Twitch?
Less than you might be expecting.
Only about 21% of all Twitch content viewed from July to December of 2015 was esports related. This adds up to about 475.5 million hours viewed across all franchises, or about 79 million hours per month.
The split for viewership varies widely based on the game. For some, the split is about 50/50, such as StarCraft II, Dota 2 and CounterStrike: Global Offensive. Other games are considered much more casual content oriented, such as League of Legends and Hearthstone, whose games' popularity sprung almost entirely from the streaming market initially.
Riot's League of Legends led the pack with the most overall content created and consumed, which is not surprising given its popularity. Despite only taking 27.3% of the overall share of its viewership, League by far had the most esports hours watched of the five games, with 17.4 million more hours watched than Dota 2, its closest competitor.
Despite the relatively small percentage of Twitch's overall viewership, it continues to be important to the company as evidenced by recent pushes into CounterStrike and Rocket League event sponsorship.