So first of all , what fully proportional means is that in a 3 seat district , a party with 33 . 3 % of the vote is guaranteed 1 seat . MMPAMS doesn ' t guarantee that . That ' s your definition of fully proportional , not a universal one . Most people think of a fully proportional system as one where a party ' s percentage of the national popular vote matches it ' s share of the seats . You could have singlemember districts with STV and it would be no more proportional than IRV . You could just as easily have your scenario happen under 10 seat AMSMMP and by just as easily I mean not very easily it ' s never actually happened in STV . I don ' t support 10 seat MMP , I support having a large number of topup seats at the national level . BTW , the Greens in Ireland won 2 . 7 % of the vote and got 2 seats out of it . So they were still underrepresented . Could you tell me where this talking point came from by any chance ? Math and history . Ireland even had a parliamentary committee in 2010 dealing with the lack of proportionality caused by 3 member districts .