How The PR "Quota" System Works

Proportional representation or PR is the form of voting used by Cambridge under the Plan E form of governemnt. Under PR a candidate needs to win a certain proportion of the the votes to be elected. This winning fraction of the votes is referred to as the "quota".

The quota is determined by dividing the total number of valid ballots cast by the number of positions to be elected plus one and then adding one to the resulting dividend.

Thus, to elect 9 City Councillors, the total number of valid ballots cast is divided by 10; to elect 6 School Committee members, the total is divided by seven. And in both cases 1 is added to the result of the division.

For example, if 25,000 valid ballots are cast for City Councillors, the quota will be 2,501 (25,000 divided by ten, plus 1).

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Last updated on June 22, 1994.
Eric Loeb (, Nancy Cheung (
Intelligent Information Infrastructure Project
Artificial Intelligence Laboratory, Massachusetts Institute of Technology