The plenary chamber of the German Bundestag from above: the seats are arranged by parliamentary group © German Bundestag

As a rule, the people determine the composition of the Bundestag every four years. The Basic Law stipulates that its Members be elected in "general, direct, free, equal and secret elections". "General" means that all German citizens are able to vote once they have reached the age of 18. The elections are "direct" because citizens vote for their representatives directly without the mediation of delegates to an electoral college.

"Free" means that no pressure of any kind may be exerted on voters. "Equal" means that each vote cast carries the same weight with respect to the composition of the Bundestag. "Secret" means that each individual must be able to vote without others learning which party or candidate he or she has chosen to support.

Constituencies and Land lists

Half of the Members of the Bundestag are elected directly from Germany’s 299 constituencies, the other half via party lists in Germany’s sixteen Länder (states). Accordingly, each voter casts two votes in the elections to the German Bundestag. The first vote, allowing voters to elect their local representatives to the Bundestag, decides which candidates are sent to Parliament from the constituencies. The second vote is cast for a party list. And it is this second vote that determines the relative strengths of the parties represented in the Bundestag.

At least 598 Members of the German Bundestag are elected in this way. In some circumstances, Parliament’s size may increase during the process of allocating the seats due to what are known as "overhang seats" and additional "balance seats".

Distribution of seats in the Bundestag

The 598 seats are distributed among the parties that have gained more than five percent of the second votes or at least three constituency seats. Each of these parties is allocated seats in the Bundestag in proportion with the number of votes it has received. In 2013, the Bundestag introduced a new method of distributing the seats between the parties, to comply with requirements set by the Federal Constitutional Court.

Germany’s electoral system, a combination of "first-past-the-post" election of constituency candidates (first votes) and proportional representation on the basis of votes for the parties’ Land lists (second votes), has been retained. However, the method by which the votes are converted into seats has changed.

Two stages, each involving two calculations

The Sainte-Laguë/Schepers method is used to convert the votes into seats, in a two-stage process with each stage involving two calculations. First, the number of seats to be allocated to each Land is calculated, based on the proportion of the German population living there. Then the seats in each Land are allocated to the party lists in that Land, based on the proportion of second votes each party received.

The minimum number of seats for each party at federal level is then determined. This is done by calculating, for each party Land list, the number of constituency seats it won on the basis of the first votes, as well as the number of seats to which it is entitled on the basis of the second votes. The higher of these two figures is the party’s minimum number of seats in that Land. Adding together the minimum number of seats to which the party is entitled in all of the Länder produces a total representing its guaranteed minimum number of seats in the country as a whole.

"Balance seats" to maintain proportionality

It is generally necessary to increase the size of the Bundestag to ensure that each party receives its guaranteed minimum number of seats when the seats are allocated using the Sainte-Laguë/Schepers method. Then it must be ensured that the seats are distributed to the parties in line with their national share of the second votes.

Additional "balance seats" are created to ensure that the distribution of the seats reflects the parties’ share of the second votes and that no party receives fewer than its guaranteed minimum number of seats. Balance seats are also necessary to ensure that each party requires roughly the same number of second votes per seat. Once the number of seats which each party is entitled to receive across the country has been determined, the seats are allocated to the parties’ individual Land lists. Each Land list must receive at least as many seats as the number of constituencies which the party won in the Land in question.

Coalition negotiations

The total of 630 seats in the Bundestag’s 18th electoral term can therefore be broken down into the 598 seats which represent the general minimum number of seats in Parliament; four "overhang seats", where a party (in this case the CDU) won more constituency seats than it would have been entitled to based on its share of the second votes, leading to 602 seats at a minimum in the 2013 elections; plus 28 balance seats to ensure the relative strengths of the parties in Parliament continue to reflect the share of second votes won. Of these additional balance seats, thirteen were allocated to the CDU, nine to the SPD, four to the Left Party and two to Alliance 90/The Greens. The CSU was the only party which was not entitled to any balance seats.

The results of the Bundestag elections determine the relative strengths of the parties in the Bundestag and therefore the options available when a government is formed. A government can only be formed by parties that, singly or together with others, have the majority of Members behind them. This is why elections are often followed by coalition negotiations between the parties. (vom/08.10.2013)