US iPhone owners spent average of $35 on apps in 2015, mostly on games

There were about 110 million active iPhones in the U.S. last year, said app marketing firm Sensor Tower, citing data from sources like Consumer Intelligence Research Partners. That figure was compared against Sensor Tower's own estimates for iPhone app downloads and revenue, since Apple rarely breaks out specific figures for the App Store.

Within the $35 tally, the lion's share of that — $25 — was spent on games. Although games are a consistently popular category at the App Store, that figure may have been inflated by so-called "free-to-play" games like Game of War and Clash Royale, which often force players to make in-app purchases to achieve real progress.

The next most popular category was music at just $3.40. Social networking, entertainment, and "lifestyle" apps attained averages of $1.80, $1, and 40 cents per iPhone, respectively, while the remaining $6.80 was split between 18 other categories.

An average of 10.5 games were installed per device, easily beating out the 3.4 from the next closest install category: photo and video. Social networking, entertainment, and lifestyle apps rounded out the top five.

Sensor Tower's study was notably narrow in scope, as it excluded iPad apps.