Imperiali quota

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The Imperiali quota is a formula used to calculate the minimum number, or quota, of votes required to capture a seat in some forms of single transferable vote or largest remainder method party-list proportional representation voting systems.

Ecuador is among the few countries that uses this allocation system, while Italy used it for its Chamber of Deputies from 1946 to 1993.

It is

$\frac{\mbox{total} \; \mbox{votes}}{\mbox{total} \; \mbox{seats}+2}$