Popularity Ranking should be based on Downloads per unit of Time
Currently popularity ranking appears to be based on number of downloads per released version. This gives the odd skew that some packs and mods are more popular than they really are.
The formula should be adjusted to be the number of downloads per unit of time such as a rolling 7 day average. This would be a far better indicator of popularity and not so easy to game as some would fear.
There are many factors that go into calculating popularity. We do not disclose these factors to prevent any fraud within the system. However I can assure you that it does not work like you think its working.