As an add-on to my earlier post, Bart Smith points me to an article on The Wrap about how nomination votes are tallied.

I found it very straightforward until the “surplus rule”:

In this case, “Up in the Air” and “Avatar” have significantly more votes than the 501 they need to be nominated, and more than the 601 (501 plus 20 percent) they need to trigger the surplus rule. “Up in the Air” has twice as many votes as it needs, and “Avatar” has 50 percent more.

So those two films get their nominations, but their ballots aren’t taken off the table. Instead, they’re all redistributed into the piles of the films listed second — where they count not as a full vote, but as whatever fraction of the vote wasn’t needed. A sliding scale determines exactly what percentage is used.

The “Up in the Air” ballots, for instance, will count as half a vote, because that film only needed half of each of its 1,002 votes to reach the magic number of 501. “Avatar” needed two-thirds of its 771 votes to reach the threshold, so its redistributed votes will count as one-third – i.e., the unneeded portion of each vote.

Each voter will still only get a single vote – but in this case, that single vote will be split between two different films.

It ultimately makes sense, but it very much feels like a system devised by accountants.