The constituency is the unit of conversion of votes into seats, normally on a territorial basis, but there are exceptions, such as the four Maori districts in New Zealand, those reserved in Portugal to its emigrants or to ethnic minorities in Bulgaria, Croatia and Slovenia. From this point of view, an overall vision of comparative constitutional law permits us to classify the countries into four large groups:
Countries that use the whole of the national territory as an electoral constituency, which in practice means asserting that for electoral purposes, territorial division does not exist. This system is characteristic of geographically small countries with a strong identity and high degree of cohesion. This is the case, for example, in Israel and Holland. It leads to extremely proportional results and, consequently, great stability of the governments. It is also a characteristic choice for the election of multinational assemblies that do not have the election of a the head of government among their functions, like the European Parliament.
Countries that use ad hoc electoral districts, periodically delimited and normally united to a majority system. As a consequence, these countries have to establish an electoral map that combines the fundamental criterion of the equal value with others that, to different degrees of intensity, aim to focus on other aspects of collective identity of the existing communities in that country and avoid an artificial political representation, alien to cultural, ethnic or other divisions, often referred to as 'communities of interests'. Problems may arise regarding the adaptation of the constituencies (originally or unexpectedly) and even of gerrymandering (politically motivated altering of boundaries of electoral districts). This procedure is used in Great Britain, in other Anglo-Saxon countries such as Canada and New Zealand as well as others influenced by them, such as Mexico.
Countries that use existing geopolitical units as constituencies, which is normally linked to proportional elections in multinominal constituencies. It can pose problems regarding equality of voter insofar as there is a great disproportion in the number of inhabitants among them. The system is applied in countries such as Italy and Spain. From an organisational point of view, it is the simplest and the most cost effecient.
States that use mixed constituencies, such as Germany and, following its example, Venezuela. The aim here is to combine the relative advantages of the large proportional systems and of the majority systems. To achieve this, a national constituency is established, with a very high electoral barrier that avoids excessive fragmentation of the chamber. The closeness among voters and those elected is maintained by the personalisation that majority systems provide. In practice, the great trouble with these systems is that they have a complex character and are difficult for the average voter to understand, especially in counties in transition.
