Facebook has changed how it calculates daily and monthly active user figures, causing titles to see huge falls in numbers.
The alterations mean users who visit an app without logging in are no longer counted.
Games hit by the change include Zynga’s Adventure World, with the monthly active user figure dropping from 39.4 million to 16. 4million, a 58 per cent drop.
Cityville’s MAU figures meanwhile have fallen from around 76 million to 55 million, and The Sims Social has plummeted from 65 million to 42 million.
The alterations have been designed to more accurately reflect app usage figures.