All of these results are not absolutely certain. This is the best evidence we have, and it's still not.... More work could be done. But unsurprisingly, I guess, when you ask specifically about perceptions of fairness, then PR clearly performs better. But when you ask for a very general evaluation of how democracy works, then it doesn't make a difference. PR helps in affecting specific perceptions of fairness, but if you think about overall evaluations of how democracy works, it's not enough. There are many other things that are taken into account, and in the end it doesn't have a significant effect, it seems.
On July 27th, 2016. See this statement in context.