Tom Round remarks at F&V:

By the way, the Proportional Representation Society of Australia’s “PR Manual” caters for very small electorates by providing for the votes to be counted (and the quota to be calculated) to four decimal places. Otherwise too many “vote points” get lost via surpluses. So, if 80 members of the “Utopia Tennis Club” are electing 5 executive committee members, the quota will be 13.334 votes rather than 14 votes, thus leaving the runner-up with 13.330 votes, rather than 10, and reducing the risk of a tie.

Ties can be a big problem in STV elections with small electorates. They can make people question the legitimacy of the system in general and an election in particular.

In one election I hand-counted, two candidates were tied for elimination, and none of the fairer, conventional tie-breaking rules helped: looking at first choices, looking at the prior round’s total, etc. We had to flip a coin. While the order of candidates’ elimination would not have changed who won in the end, the failure of all tie-breaking conventions and having to resort to a coin raised a lot of ire. There were somewhere around 12 voters and two winners to elect.

So calculating the quota (or victory threshold) out to four decimal places seems like a good idea. In general with the single transferable vote, the more numerical precision, the “fairer” the result. But how does one manage fractional thresholds when counting by hand?

It’s doable (as are fractional transfers) but laborious. Apparently OpenSTV will do it for you when you tell it to use GPCA rules.