dHondtJefferson

dHondtJefferson is a term used in the theory of apportionment to describe the relationship between two divisor-based methods for allocating legislative seats: the d'Hondt highest-averages method and the Jefferson method. Both methods aim to distribute a fixed number of seats among parties in proportion to their votes, but they derive the allocation through different procedures that are closely connected within the broader family of divisor methods.

The d'Hondt method assigns seats one by one by computing quotients for each party as votes_i divided by (s_i + 1), where s_i is the current number of seats for party i, and then giving the next seat to the party with the largest quotient. The Jefferson method fixes a common divisor D and assigns seats_i = floor(votes_i × S / D); D is chosen so that the total seats equal S. For many elections, the resulting seat counts from the Jefferson method can be replicated by the d'Hondt process with a suitable divisor, illustrating their equivalence as a family of divisor methods. Ties may occur and require predefined rules.

In practice, methods in this family are praised for monotonicity and relative computational simplicity, but are known to exhibit a bias toward larger parties compared with some quota-based methods. The d'Hondt/Jefferson framework underlies procedures used in several countries for parliamentary apportionment, and discussions of it focus on properties such as proportionality, bias, and stability under changing vote totals.