The much-awaited Eden-Monaro preference flows are finally out, following some time after the distribution of preferences, and it's useful to make some comments about these. (Also see Antony Green's comments.)
Labor won the by-election by 735 votes (50.39% 2PP). This means that had 368 voters who preferenced Kristy McBain instead preferenced Fiona Kotvojs, Kotvojs would have won. This is relevant for checking various claims about preferences of particular parties deciding the result. In my Eden-Monaro live thread I set some markers at the time for particular preference shifts causing or not causing the result.
Did Nationals preference flows weakening cause Labor to win?
Answer: Yes - but this isn't necessarily what it looks like. In Eden-Monaro in 2019 an unusually strong 87.16% of Nationals preferences flowed to Fiona Kotvojs. At the 2020 by-election the flow was only 77.73%, making a difference of 571 votes to each side's total, and a difference of double that to the margin. While it was unrealistic for the very high flow from 2019 to have been maintained, any flow above 81.08% would have resulted in the Liberals winning the seat. That figure is almost exactly the 2019 national average in contests where the Nationals were excluded, so the switch from an above-average to a below-average Nationals to Liberals preference flow can be said to have cost the Liberals the seat.