Oscar 2009: How Does the Preferential System Work?

The Academy of Motion Picture Arts & Sciences (AMPAS) consists of 15 branches. Voters nominate achievements in their own branch (directors nominate directors, editors nom editors, etc.). All members vote for the top prize, Best Picture.
Nomination ballots will be mailed December 28, and voters will receive a card with five blank spaces (in most categories) to fill in their top five choices.
This year, the best-picture category features 10 blank spaces because of the expanded number of noms. Some voters mistakenly believe all 10 will count for something. But only one of them will, andi it may not be their first choice.
PricewaterhouseCoopers executives Brad Oltmanns and Rick Rosas explained the system. Take the Directors branch, which has 375 voting members as of 2008.   The accountants take the number of possible nominees in that category, five, and add one.
That total, six, is divided into the 375, which yields the number of 63. In round one of nomination tallies, the PWC folks take all the directors’ ballots and count up voters’ first-place choices: Any contender who earns 63 votes has enough for a nomination. The PWC then set aside the ballots of those members who voted for that director, never to look at the other choices, because that voter’s voice has been heard.
Round two: They take the stack with the fewest number of votes, and look at the second choice, and redistribute the ballots among the stacks. However, if a voter picked a director who had already hit the magic number, they go to the voter’s next choice. For each round, they look to a voter’s next highest choice — second, third, fourth, fifth — so long as that director remains in the running and has not otherwise hit the magic number.
The Academy is the only awards group that uses what’s called preferential voting. The Academy has been using it since 1936.
It’s designed to deal with elections in which there is more than one result (five director nominees rather than a single winner).
The preferential system is not a “weighted ballot.” That system gives different points for different slots (10 points for first place, eight for second, etc.). 
It doesn’t help your candidate if you fill out only one line, or fill the same name/title in all five slots.
There are five categories that vote by committee: two short subjects, two documentaries and foreign-language.
After the AMPAS nomination deadline, on January 23, 2010, PricewaterhouseCooper’s experts assemble all the ballots. In most of the categories, it will be straightforward counting: The person with the most votes wins.
But for best picture, there are 10 noms. So the preferential system will be used again. And, you may ask, in a world that’s already complicated, why are they making things more difficult? Why not just go with the first-place vote? Excellent question.
By using the preferential system here, PWC and the Acad avoid the possibility of a film winning with only 11% of the votes and avoid the possibility of a tie.
The PWC form 10 piles for best picture, one for each film. They go through the first-place choices. And the film with the lowest number of first-place votes is eliminated. Then they take the nine remaining films, and go through the second-place choices. Again, the lowest vote-getter is eliminated. In all, they will do eight rounds of this. At the end, the winning film will have 50% of the votes — plus one.