• by Gavin O'Malley  @mp_gavin, February 26, 2018

While making headway in terms of both user retention rates and engagement, app developers continue to struggle on both fronts. On average, just 13% of users returned to apps 14 days after downloading them last year, according to a new report from Adjust.

For its findings, the Berlin-based mobile measurement firm analyzed 11,000 apps -- which comprised 10.7 billion installs and 1.29 trillion events -- throughout 2017.  

On average, iOS app retention rates were better than those of Android apps -- but only by 1%-to-3%. Utilities apps were used the most -- with three sessions per day -- last year.

For reasons that should be obvious to anyone who’s ever played Candy Crush, gaming and entertainment apps remained top engagers. Thirty days after they were downloaded, entertainment apps saw the highest retention rates, on average.

Due to the cyclical nature of travel booking, travel apps had the most trouble keeping users’ attention. Twelve days after being downloaded, this category of apps suffered from a 7% retention rate, on average. In total, another 2 million apps were released across iOS and Android platforms, last year.

Worldwide, mobile ad spending increased 33.6% -- up to $142 billion -- with $17 billion being spent on performance ads.

Google and Facebook drove half of all attribution, while Google’s network seemed to be a slightly the better option to reach and engage users, by Adjust reckoning.

Mobile ad fraud remained a huge problem last year, especially for Android users. Indeed, twice as much mobile fraud occurred on the Google-owned platform. Andreas Naumann, at fraud specialist at Adjust’, attributes Android's vulnerability to “click injection” -- a sophisticated form of click-spamming, which apparently only affects Android devices.

By vertical, games were the most affected by fraud, last year. In fact, over one-third of fraud stopped by Adjust targeted gaming apps.

That was partly due to gaming apps spending more on mobile marketing than any other category, the measurement firm notes.