Reasons for Overhang seats [this page in German] [Overhang Seats Page]

The Mixed Member Proportional representation (MMP / AMS) tries to link two (partially opposed) principles:

For each candidate directly elected in the constituency his party list will lose a seat. Hence, it is mostly worthless to win a constituency and the constituency vote is not useful for parties.

But this only works, as long as the party wins more seats by the party vote (secondary vote) than by the first vote (constituency vote).

If a Party is awarded less seats, as it needs to justify the constituency seats won, the missing proportional seats are additionaly awarded as additional overhang seats (see § 6 Abs. 5 and § 7 Abs. 3 sentence 2 BWahlG).

The two direct reasons, increasing the number of overhang seats of a party's Land's List, are:
1. Several won constituencies.
2. Few Party votes.

The week point in the legitimation of overhang seats is Reason 2: few or missing votes cause additional seats.

All other conceivable reasons cause overhang seats by changing reason one or two:

von Martin Fehndrich