Popularity reflects the image of your club near the general public at one given moment.

Very fluctuating, it strongly depends on your “successes of the moment”, and can be comparable with specific overall placings.
To improve its club or to gain a championship makes it possible to make leap its notoriety ; while to wipe a demolished cuisante the adverse effect produces. In the same way, the inaction erodes your prestige naturally : crowd quickly forgets the last exploits !

A strong popularity makes it possible to attract members, improves environment of the room and supports moral your champions. It is a good indicator of your capacities of manager (and also of possible bad lucks !).