The Universities of Southern California (USC) and Indiana conducted a study of Twitter's bot population. After using about 1,000 features across 6 categories, they found that 9 to 15 percent of the site's monthly users are bots. That estimate puts the bot population anywhere between 28.7 to 47.9 million accounts. Twitter's spokesperson referred to a February filing made to the Securities and Exchange Commission that it estimates 8.5 percent of accounts to be automated. Last year, USC also found that a wealth of election-related tweets were from bots and not humans.