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We already know bots have a significant presence on Twitter.

But a report published Monday by the Pew Research Center suggests automated accounts are more prevalent than we may previously have thought.

Pew estimates that two-thirds, or about 66 percent, of the links shared on Twitter come from bots rather than people. The research specifically focused on the 2,315 most popular websites and over 1 million tweets sent between July 27 and Sept. 11, 2017.

The 500 most active supposed automated accounts represented 22 percent of the links tweeted to popular sites, whereas the 500 most active human accounts made up just 6 percent of the links tweeted to the same sites.

Pew did not find evidence of political bias among the suspected bots. Read more about Pew's research methodology here.

A Twitter spokesperson explained that it is not possible to accurately determine whether an account is automated or human-run. Read Twitter's blog post about how it treats bots.