The Question

This question is posted on behalf of Dr. Ipek Eren Vural, an academic from the Middle East Technical University, Ankara, Turkey.

My question is about the apportionment formulas of parliamentary/assembly seats. Are there any countries (except Lesotho) which use the criteria of voting age population, registered voters, or actual voters (as opposed to total population) during the apportionment of parliamentary/assembly seats?

Summary of responses
According to a study conducted in 2005-06 (see External Resources below) 34 per cent of the countries surveyed used the number of registered voters as the criterion to apportion parliamentary seats. Only Lesotho was found to use voting age population, while Belarus used the number of voters from the previous election.

Another practitioner notes that Mozambique apportions its seats based on the number of registered voters in the country’s provinces. And in Tanzania, seats reserved for women are allocated according to the number of valid votes a party receives.

Examples of related ACE Articles and Resources
Encyclopaedia:
• Allocating Seats 
• Use of Population Data in the Delimitation Process 

Consolidated replies:
• Methods of Apportionment 

External Resources
• Delimitation Equity Project Resource Guide, Lisa Handley et al. (IFES)

Names of contributors
1. Staffan Darnolf
2. Marc De Tollenaere
3. Amon Emmanuel Chaligha
4. Lisa Handley

I would suggest you have a look at the Delimitation Equity Project lead by Dr. Lisa Handley. You'll find data from this study by simply Google it.

Staffan

Mozambiqiue distributes its 250 parliamentary seats proportionally based on the number of voters registered in each of the 11 provinces

marc

Tanzania uses first past the post for apportioning parliamentary constituency seats. However, for women special seats  the allocation is proportionally made according to the number of valid votes a party receives. For a political party to qualify it must secure a minimum threshold of 5 percent of all total votes cast in a particular election. Each contesting political party must provide a list of names of women to the National Electoral Commission which will scrutinize their qualifications. After the results of constituency seats are announced, the National Electoral Commission then announces the names of women who have been  proportionally selected from the political party lists.  

A majority (53 percent) of the countries I surveyed for an IFES study conducted in 2005-2006 (see Delimitation Equity Project Resource Guide found on the IFES website) indicated that “total population” was the population base used for determining equality across constituencies (e.g., Botswana, Canada, France, India, Japan, Kenya, Mexico, New Zealand, Pakistan, Uganada and USA).  Another 34 percent reported registered voters as the population base (e.g., Armenia, Australia, Bahamas, United Kingdom, Croatia, Iceland, Namibia, Slovakia, Ukraine, and Zimbabwe). Six countries (almost all European) stated that citizen population was the relevant base for determining population equality. The voting age population was mentioned as the base by one country (Lesotho), and the number of voters in the previous election by

another country (Belarus).