The research group found that the dollar amount spent on apps and in-app purchases is continuing to increase, year-over-year. iPhone users spent an average of $63 this year, up 33% over 2016. By 2019, the increase over 2016 will have grown to 86%, predicts Sensor Tower. In 2018, the research group estimates the average spending per active U.S. device will grow to $77, before reaching $88 by 2020. The majority of spending — almost 70 percent — will come from games. As much as $60 of that $88 will be on paid game downloads and in-game purchases.