How do services like AppAnnie come up with retention data?

Question

Many third party services (e.g. AppAnnie) can show retention data for (almost?) every app out there. How do they do that? They can't have first party data access to every app. Are there ways to build heuristics to calculate retention data with public infos from the app stores?

Answer 1

App Annie and Sensor Tower operate VPN apps that are used to collect app usage data:

Your VPN or ad-blocker app could be collecting your data

You're right that they can't collect first-party data for every single app that way, and the metrics those companies share around retention, monetization, and DAUs are mostly modeled based on fairly limited source data.