According to Sensor Tower US iPhone users spend and average of $40 on apps during 2016, but the total number of apps being installed on their iphones are falling, where in 2015, the average number of downloads were at 10.5 and the report states that for 2016 the avg. number of game apps downloaded fell down to 9.9 games.
As User Acquisition becomes more and more competitive landscape this data doesn’t not bode well for publishers as UA cost is inevitably going to rise at a faster pace if players aren’t downloading as many apps they have in the previous year.
Based on further research, there are actively 132 million active iPhones in the US. and the main source of IAP is games where out of the $40, $27 comes from IAP for games.