A report from IDC said mobile device users have installed nearly 156 billion mobile applications in 2015, generating $34.2 billion in direct (non-advertising) revenue.

The number of mobile applications will grow to more than 210 billion generating nearly $57 billion in direct revenue in 2020.

IDC expects to see slower growth in both application install volumes and direct revenue over time — largely driven by market maturation.

Mobile application install volume will experience a five year compound annual growth rate (CAGR) of 6.3 percent. Direct revenue from mobile applications will experience slower growth by the end of 2020, though the five year CAGR will be 10.6 percent.

Apple’s App Store captured nearly 58 percent (+36 percent) of direct app revenue in 2015. Apple’s share of app install volume was 15 percent, down nearly 8 percent. Google Play captured about 60 percent of install volume and nearly 36 percent of direct revenue in 2015.

Growth of Google Play’s downloads and direct revenues were lower than in previous years. Apple is expected to continue outperforming Google Play in terms of revenue generation.

“Facebook and Google continue to dominate mobile ad spending thanks to the scale and sophistication of their network effects, with Facebook’s moves to incorporate news and other interests into its experience will likely pull traffic and install volumes away from discreet apps,” said John Jackson, research vice president, Mobile and Connected Platforms at IDC.

The IDC report noted that the emergence of bots, which seek to automate interactions in a contextually infused way, are another in a series of examples of value being created above the OS layer and even above the app.