Andrew Chen posted an interesting article on App retention: New data shows losing 80% of mobile users is normal, and why the best apps do better.
The main giveaway is: the average Android app loses 77% of users in the first 3 days, where the top 10 apps, only loses 30%.
Here's the cohort chart of the average Android app:
Curious about your apps? In Google Analytics (and other analytics tools) you can get the same chart:
It's clear that the main challenge in app adoption is user activation. You should focus on getting it right, have a good onboarding experience and quickly return value to users. Because after a week, no notification will change their mind.