Games : What is the average stat change after Pokemon Evolution? [on hold]

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.

For example, Bulbasaur has base stats of 45 49 49 65 65 45. Ivysaur's base stats are 60 62 63 80 80 60 and the differnces are 15 14 15 15 15 15. What I want to know is the average change across all Pokemon using this method of calculation.