What percentage swing needed to win a vote? (This seemed like a no-brainer, but I'm throwing my hands up...) Australia is having a national "postal survey" about same-sex marriage. * The options on the ballot paper are "Yes" and "No", but voting is not compulsory. * The survey is being conducted over 8 weeks during which eligible voters can return their response. * At the end of the third week, 60% of voters have returned their response. * Exit-polling indicates of those who have already voted, 60% voted "Yes" and 40% voted "No". **Question** : All other things being equal (e.g. early/late responders no indication of which way they vote) what % of the remaining 40% who haven't returned their response would need to vote "No" in order to achieve parity with the "Yes" vote (here's the kicker...) taking into account that not all eligible voters will ultimately return their ballots? Is this work-outable?

If the final vote turn-out was approximately 100%, then the remaining voters would have to split approximately 35% Yes, to 65% No to swing the total to No.

If the final vote turn-out was approximately 72%, then the remaining voters would have to split approximately 0% Yes, to 100% No to swing the total to No.

If the final vote turn-out was less than approximately 72%, then there is no way to swing the total to No.

**(Off-topic-note: I can only hope that the referendum is binding and Australia can finally join the 20th century in this matter).**