Amazon’s cashierless Go stores could be a $4 billion business by 2021.

Amazon’s cashierless Go stores could be a $4 billion business by 2021. That estimate comes from RBC Capital Market analysts, who used the current number of visitors to Go stores—550 a day—to work their math. Amazon has plans to open as many as 3,000 locations in the next three years. Young consumers ain’t got time for waiting in line at stores, with 47% of 13-35-year-olds telling Ypulse they have left a store because the checkout wait was too long, so the concept of quicker in-store experiences will likely resonate. (Recode)