It doesn't work. It can't work. Utopian ideals always end the same way: imposed only through tyranny.
Every study I've read by proponents starts from a view that it will work or must have a manner of working that is yet to be discovered because it meets the fundamental criteria of all their political beliefs; namely that all people are victims being oppressed by economic systems. Which is of course not true.
As with almost all "social science" studies, these are easily designed to prove whatever the author needs to.