There is such a system in place actually [0]. It is believed that the playerbase is separated into pools [1] somewhat based of this number. How it is calculated is anyone's guess.
[0] https://www.reddit.com/r/DotA2/comments/46y4v8/dota_2_behavi...
[1] https://www.reddit.com/r/DotA2/comments/351mdk/discussion_do...