I ' m assuming the common choice of 5 member districts , yes , as I ' ve stated repeatedly . First time you ' ve told me though . I ' ve been left to wonder why you insist that STV has an 20 % difference from proportionality first you said 16 %, so I thought you were talking about a 6 member district , and the only thing I could think of was that you imagined STV as being specifically 5 member for some strange reason because of the inherent relationship between 20 % and 15 . If you are going to assume 5 member districts for STV , you also need to do that for the system you are comparing it against in order to talk about the proportionality of the systems . There is no fundamental property of STV that makes it work differently with 5 member districts than 50 or 500 member districts . STV covers all of those cases . STV is to PAV or PR what IRV is to Approval or FPTP . The fact that some people like it better with smaller districts is irrelevant .