I recently got to know that Android has captured 97% of the market share in India. Source. Out of all the smartphone users in India, they are using some version of the Android app. This means that you definitely need to target Android users first when you are making a mobile app for your business.
iOS users are the ones from whom you will generate more revenue as they are the ones who spend money on apps as opposed to Adnroid users. Reason is that the iOS users are from an income group which is higher than the average Android user base. Android users are more used to free apps as the play store is cluttered with sub standard free apps.
If you have an idea which would mean a stand alone mobile app, you do need to target iOS users also but Android should be the first OS which you should target as it is easier to test and fast to update the app than iOS.
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