The average US iPhone owner spent $40 in App Store purchases during 2016

The bulk of the increase was due in large part to games, which grew to represent 80 percent of Apple's U.S. App Store revenue, Sensor Tower said this week. That translates to about $27 per device, a growth from $25 in 2015.

Spending in the "Entertainment" category was also up from an average of $1 in 2015 to $2.30. This is thought to be linked to the popularity of video services like Netflix, Hulu, and HBO Now — Netflix's contribution to revenue amounted to $58 million during the December quarter alone.

Other categories like Social Networking and Photo & Video also grew. One standout was Music, which rose from $3.40 to $3.60. That includes streaming services like Apple Music, Pandora, and Spotify.

Sensor Tower noted, however, that the average number of installed apps actually shrank, dipping from 35 to 33. That could be bad news for incoming developers, since users are reportedly sticking to the store's most popular apps such as Facebook and Snapchat.

The firm's conclusions are based on data from 132 million iPhones, as well as figures from other sources like Consumer Intelligence Research Partners. 30 percent of the quoted revenue is also going straight to Apple, rather than developers or service providers.