At 50%, do you start fudging numbers to ensure you go no higher? "No, Senator, we are not the majority of users, so we can't be a monopoly." Or maybe that's too immoral, so start funding the other(s) to prop them up? Microsoft propped up Apple to ensure there were other consumer OS makers with Apple being the most viable* competitor.

*viable is doing a lot of heavy lifting as they did need that propping up