The Best Way to Cut an Email Thread, According to Computer Science

If you’re caught in an interminable email conversation, the best way to cut the thread is a short response after a long delay. Not only does a curt “Got it!” after 12 hours of radio silence make sense as a cheery yet nigh insurmountable conversational impasse, the underlying principle is supported by a predictive model computer scientists have built based on the email conversations of two million Yahoo users.

“When there’s a very short email there’s a lower chance of a response,” Farshad Kooti, a Ph.D. student and computer scientist at the University of Southern California, tells Inverse. It makes sense, as there’s not that much information that needs to be processed. After a “thank you!” or “great!” he points out, people don’t really have an incentive to reply.

Kooti and his colleagues crunched 16 billion emails to build the predictive model that factored length of the emails, how long email chains went on, the age of the users, and the volume of emails received. A few trends bubbled to the surface: Teenagers take, on average, 13 minutes to reply, whereas people over the age of 51 waited, on average, 47 minutes. The speed of replies reaches a rough equilibrium around the halfway point of an email conversation. If you’re a slow replier, you pick up the pace when emailing someone who is faster to respond. That said, response rates diverge at around the same time based, to a degree at least, on the age of the respondents. Younger emailers tend to shorten their responses whereas older emailers continue to write longer notes, but leave more emails unanswered.

Evening and weekend emails had a worse chance of a reply — though given their after-hours existence, Kooti says, that means they could be social or less pressing than a work-related correspondence.

Using this data, the scientists created an algorithm that could predict the last email in the chain 66 percent of the time. Kooti hopes to use this study as a launching point for better email sorting. “Right now emails are ranked in chronological order,” Kooti says. If you could instead predict which emails would be most likely to precipitate a response, and put those at the top of an inbox, you could help people cut through the chaff.

Want to up the odds that a conversation keeps going? Toss in an attachment. “Emails that have an attachment usually get longer replies,” Kooti says. “The chance of getting a reply increases.”

To synthesize: If you don’t want more emails, lose the attachments, slow your reply time way down, wait for extracurricular hours, and limit your response as much as possible. Just don’t reply “Thanks.” with a period like an asshole.