One major problem is that most voting carries only ordinal data (preference ranking), not cardinal (magnitude of preference). And the ones that allow aggregation or magnitude are very susceptible to strategy. This makes utilitarian optimization among uncooperative members very difficult.
STAR voting largely solves this problem, by taking the runoff idea from ordinal voting and applying it to cardinal voting.
The idea is this: your ballot is just like cardinal voting. You find the top two candidates by total score. Then you choose the candidate who would win in a pairwise election between the two, under the assumption that you’d vote for whoever you gave a higher score, and abstain otherwise.
This incentivises voters to score different candidates differently, unless they really don’t care between two, because otherwise you could be throwing away your vote in the final stage.
As a result, STAR does better at collecting the utilitarian preferences, but at the cost of sometimes choosing a candidate other than the utilitarian max. (But arguably, choosing someone who would win in a pairwise election against the utilitarian max isn’t too bad—to win against the utilitarian max in a pairwise election, you have to be more of a compromise candidate, meaning STAR favors more equitable outcomes.)
One major problem is that most voting carries only ordinal data (preference ranking), not cardinal (magnitude of preference). And the ones that allow aggregation or magnitude are very susceptible to strategy. This makes utilitarian optimization among uncooperative members very difficult.
STAR voting largely solves this problem, by taking the runoff idea from ordinal voting and applying it to cardinal voting.
The idea is this: your ballot is just like cardinal voting. You find the top two candidates by total score. Then you choose the candidate who would win in a pairwise election between the two, under the assumption that you’d vote for whoever you gave a higher score, and abstain otherwise.
This incentivises voters to score different candidates differently, unless they really don’t care between two, because otherwise you could be throwing away your vote in the final stage.
As a result, STAR does better at collecting the utilitarian preferences, but at the cost of sometimes choosing a candidate other than the utilitarian max. (But arguably, choosing someone who would win in a pairwise election against the utilitarian max isn’t too bad—to win against the utilitarian max in a pairwise election, you have to be more of a compromise candidate, meaning STAR favors more equitable outcomes.)