DHondt

The D'Hondt method, named after the Belgian mathematician Victor D'Hondt, is a highest-averages method used to allocate seats in party-list proportional representation elections. It is a divisor method: for each party i with vote total v_i, quotients are computed as v_i divided by a sequence of divisors 1, 2, 3, and so on, and seats are awarded one by one to the party with the current highest quotient until all seats are filled. Equivalently, the method can be implemented by selecting a common divisor D and giving each party floor(v_i / D) seats, with D chosen so that the total equals the number of seats.

The D'Hondt method tends to favor larger parties relative to some other proportional methods, while still aiming for proportionality with the vote shares. It is simple to compute and widely used in many countries for national and regional legislatures. Notable adopters include the Netherlands, Spain, and Belgium; several other countries have used D'Hondt in various electoral systems or subnational contests.

In mathematical literature the method is often described as Jefferson's divisor method, since it is equivalent to Jefferson's approach to apportionment. The D'Hondt rule remains a common default for party-list elections because of its transparent allocation process, though it can disadvantage very small parties in elections with high district magnitudes or high thresholds.