These talks will be self-contained presentations of mathematical concepts
and theorems. They are intended to be accessible to all mathematics students.
Tuesday 25th May, 2004
1 pm, S14
Two Statistical Laws of Elections
Dr Ravi Phatarfod
School of Mathematical Sciences
Monash University
When an election is nigh, as it happens to be the case now, one sees
electoral pendulums of the type shown here, in the newspapers informing
us that if one of the parties, say Labor were to increase their vote by
x% say, they would capture y number of seats, and thus form the
Government. The relation between the x% and the y number of seats is
the obvious one as indicated by the swing of the pendulum. The
prediction rarely comes true. A more scientifically based relation
between the number of seats won and the two-party preferred vote is as
follows: The proportion of seats won by the victorious party varies as
the cube of the proportion of the votes cast for the party over the
country as a whole. This is the law of Cubic Proportions, and in the
first part of the talk we examine why the law applies.
In the second part of the talk, we consider the decision making process
involved when a group of people such as an electorate, a jury, or a
university department votes. We show why a minority of resolute
participants more or less determine the outcome of a proposition they
are voting on. This is the square-root law of the resolute minority.
Convenor: Matthew Ovens