Imperiali quota

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. It is distinct from the Imperiali method, a type of highest average method. It is named after Belgian senator Pierre Imperiali.

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

If many party lists poll just over the Imperiali quota, it is possible for this method to distribute more seats than there are vacancies to fill (this is not possible with the Hare or Droop quotas). If this occurs, the result needs to be recalculated with a higher quota (usually the Droop quota). If it does not happen, Imperiali usually distributes seats in a similar fashion to the D'Hondt method—i.e., favouring larger parties.

Formula

The Imperiali quota may be given as:

  • Total votes = the total valid poll; that is, the number of valid (unspoilt) votes cast in an election.
  • Total seats = the total number of seats to be filled in the election.