Joined: 16 Jun 06
12 Jul 09 7:41 am
Gravity just refers to the number of active affiliates who are promoting the product. The popularity is a measure of... it's popularity!
Clickbank have their own algorithm for determining this. It has to do with number of sales, commission price, refund rate and gravity. At least that's how it looks to me, there could be more to it, but knowing Clickbank I'm sure it's quite simple :)