Games : What is the average stat change after Pokemon Evolution?

There's a pokemon I think should evolve, so I'm making my own fake one, and I'm doing everything about it, like base stats and move pool and all. So what I want to know is how much does each base stat change after a pokemon evolves Ex. Bulbasuar has base stats 45 49 49 65 65 45. Ivysoar's basestats are 60 62 63 80 80 60 and the differnces are 15 14 15 15 15 15 and like that, but just the average of all evolution changes