Gaming remains a popular app category, but a recent study finds the outlook for gaming apps isn't all sunshine and rainbows.

Recent research from Sensor Tower found that games were easily the most downloaded mobile app category worldwide in Q3 2017 for both Android and iOS app stores.

But a study from Flurry analyzed the usage of apps based on their category and found that the usage of gaming apps declined by 16% globally in 2017. (Flurry defined usage as when a user opened an app and recorded what they described as a "session.")

Flurry found that the big winners, in terms of usage, were shopping apps and those that delivered digital content like music and other forms of entertainment.

Usage rates for shopping apps grew by 54% in 2017, while the usage of music, media and entertainment apps jumped by 43% over the same timeframe.

Flurry noted that the shopping app category's growth was largely due to consumers shifting their shopping behavior from the desktop environment to native mobile apps.

Reticence among consumers about using their smartphones to make purchases is fading. At the same time, smart design functions offered by apps—such as ending the need to log in to an account and the integration of digital payment services like Apple Pay—have eliminated friction points for consumers along the path to purchase.

Meanwhile, gaming app usage has been on a decline since 2015, by Flurry's measure. In data released in June 2017, the firm noted that arcade and casual games accounted for a shrinking share of gaming sessions.

But Flurry also noted that, while the number of gaming sessions was in decline, the amount of time spent gaming in the US increased from 2016 to 2017.

That means that Sensor Tower's data is not necessarily out of step with Flurry's research. Instead, it's likely that users are downloading more games but are simply playing them less.

Trends seen in gaming apps hold an important lesson for mobile app marketers, who need to look beyond downloads as a way to measure the success of install campaigns. A more useful way of considering whether app install campaigns are fruitful is by developing methods to measure things like engagement levels and lifetime value.

According to mobile ad performance benchmark data provided to eMarketer from Liftoff, the average mobile app cost per install worldwide was $4.12 in 2017. That figure was higher in North America than any other region examined by Liftoff, at an average cost of $6.06 per install.