Looking at the Steam Community page on my inventory, I can see that any community item such as a profile background, trading cards or emoticon can be converted into a certain amount of gems.
However, I never entirely understood what defines this value. What I have noticed is that the more popular its respective game is, the more valuable the item will be in gems. But if that's the case, what defines that game as being popular? How many times it's been purchased, the amount of reviews? And what about any base values?
How are the gem values calculated?