According to an extensive study commissioned by the Global Privacy Enforcement Network the privacy practices of app publishers often leave something to be desired.
In 59% of the cases the respective app publisher failed to inform the user about the app's data collection pre-installation, and nearly one third of the sampled apps sought permission to access information that the researchers felt was irrelevant to the apps' functionality. In the end, no more than a sobering 15% of the examined apps were found to be sufficiently transparent about what information they would gather and how it would be used.
This chart shows what types of user data smartphone apps typically request access to.
You will find more statistics at Statista