There is a percentage too.
Trophies
Trophies will now have a rarity level. They are split into four categories: common, rare, very rare, ultra rare. Each trophy will have a percentage assigned to it that shows what percentage of people who played that game earned that trophy. This adds another layer of competition to the trophy collecting culture.
http://communityvoices.post-gazette.com/arts-entertainment-living/the-game-guy/item/37552-ps4-ui-revealed










