One might have thought that Apple's app economy might lose steam as the number of Android devices began to vastly outpace those running iOS. One would be wrong.

Even as Android now accounts for 9 out of every 10 phones, Apple's store has continued to outpace Google's because Apple users spend so much more on content than their Android brethren.

Data: App Annie; Chart: Lazaro Gamio / Axios

A new report says that Apple's lead over Google should continue for the next four years, at least. App Annie projects that consumers will spend $60 billion on the Apple App Store in 2021, compared to $42 billion for the Google Play store.

If you count third-party Android stores, though, Apple is expected to finally lose its lead this year. App Annie sees Apple's App Store generating $40 billion in consumer spending, Google Play brining in $21 billion and third-party Android stores accounting for $20 billion.

Among the other findings:

• Total app downloads should exceed 352 billion in 2021, generating consumer spending of more than $139 billion.
• Of that, $105 billion will come from games
• In 2016, games represented 11% of time spent in Android apps and 39% of all app downloads, yet generated 81% of consumer spend via stores
• China will remain the largest market, accounting for more than $56 billion in app sales by 2021.