The value of U.S. proximity mobile payment transactions will total $49.29 billion in 2017, up 78.1 percent from last year, according to a study from eMarketer.

Though the growth rate will remain in double digits through the forecast period, it will slow down to 23.9 percent in 2021. That year, eMarketer predicts, U.S. consumers will use their mobile phones to pay for $189.97 billion worth of goods and services at a physical point of sale.

The average annual spend per proximity mobile payment user in the U.S. will reach $1,026 in 2017, surpassing $1,000 for the first time. That figure will continue to grow through 2021, when it will reach $2,646, according to the study.

EMarketer defines a proximity mobile payment as a POS transaction made by scanning, tapping, swiping or checking in with a mobile device. It excludes purchases of digital goods on mobile devices, purchases made online via mobile devices and purchases made via tablets.