What is ratings velocity?
Ratings velocity is how fast an app gains new ratings — a proxy for how many people are installing it now, since neither store publishes downloads.
A rating count is a lifetime total; velocity is its slope. An app with 50,000 ratings gained mostly years ago is fading; one with 5,000 gained this quarter is growing.
Across a niche's leaders, velocity is one of the best public signs of whether the niche itself is growing.