Title: Electoral methods and the probability of the Alabama paradox
Speaker: Svante Linusson (KTH, Stockholm, Sweden)
Date: 29 January 2016
Time: 3:30 – 4:30 pm
Venue: LH-1, Mathematics Department
There exists various possible methods to distribute seats
proportionally between states (or parties) in a parliament. In the first half
of the talk I will describe some often used methods and discuss their pros and
cons (it’s all in the rounding).
One easy method is called Hamilton’s method (also known as the method of
largest reminder or Hare’s method). It suffers from a drawback called the
Alabama paradox, which e.g. made USA abandon it for the distribution of seats in
the house of representatives between states. It is still in use in many other
countries including Sweden.
In the second half of the talk I will describe a joint work with Svante Janson
(Uppsala Univ.) where we study the probability that the Alabama paradox will
happen. We give, under certain assumptions, a closed formula for the
probability that the Alabama paradox occurs given the vector $p_1,\dots,p_m$ of
relative sizes of the states.