A research by Stanford University did a study with 503 call center employees of travel agency CTrip. They were divided in half: one group worked from home four days out of five per week, and the other half worked full-time at the office. After nine months, the remote working group saw an increase of 13% in performance and 9% in their overall work calling time compared to the office group. A big part of the reason was that the former group needed less breaks and had less sick days.
More information: https://recruitee.com/blog/how-to-adjust-your-recruitment-strategy-to-hiring-remote-workers/