Formal study: How many points networks share

After the thread a couple of weeks ago on how many nexuses are needed for the Internet to work, the MIB (actually a woman, but that's a different thread) asked if there were any formal studies. Have any providers done a formal study of how many points they share in common with other networks? I know most providers consider their competition, if nothing else for how peering will be done. There seems to be a tremendous amount of overlap between networks. Almost every major network map looks identical. And there are some third-party consultants selling network maps. But I was wondering if anyone had a formal study from "the horses mouth."