An interesting study by Kantar Worldpanel (https://www.kantarworldpanel.com/global/smartphone-os-market-share/) shows the trend of the market share of mobile operating systems starting in January 2012.
Android is currently, without doubt, the most popular platform, thanks to the presence on the market of several inexpensive devices and at the same time with good performance.
Windows Phone, at least in Italy, although slightly down, has passed incredibly iOS, probably due to the different models of Nokia Lumia cheap Sponsored by telephone operators.
iOS is instead a slight decrease in spite of the interesting new features available with the iPhone 5s (see, for example, the biometric fingerprint recognition).
The data obtained by analyzing in more detail the study of Kantar WorldPanel allow you to better define the business model and the target of the app that you want to accomplish. For those who , like me, has as its core business the creation of apps for mobile devices, Android is certainly the first platform to be considered, given the wide spread. However , iOS is still the platform with greater appeal to those app aimed at a more demanding public and with greater disposable income . Windos Phone instead is losing its role as a platform of "reserve" and , hopefully, in the near future will lead to results comparable to those of the other two reference platforms . Finally, bringing up the rear , Blackberry, now used only by a few nostalgic , no longer an attractive market in which to invest .
I leave you with the results of the market share for the U.S. and major European countries: