Spend in Android stores is set to overtake the iOS App Store in 2017, according to App Annie.
The analytics firm has released its 2016 to 2021 Market Forecast, which studies the trends and growth of the app economy for the next five years.
As well as suggesting increased spend, App Annie predicts downloads on Android stores will grow to 292.6 billion in 2021. That said, Apple's App Store will remain the top grossing single store of all, generating $60.3 billion in 2021.
Google Play is expected generate $42 billion, while other third-party stores will make $36 billion - meaning Android stores will make $18 billion more combined than the App Store.
Overall for 2021, the firm believes that mobile downloads will reach 352 billion and generate over $139 billion in revenues. This is due to estimates for 2016's mobile revenue being 15.1% higher than App Annie originally predicted.
India is also set to grow rapidly over the next five years. It is predicted to reach 23 billion app downloads in 2021, although the region will generate just 2% of all revenues globally.
China, however, will see its revenues grow by 24% between 2016 and 2021. This will help it account for 41% of the global app economy's revenues.