What if we had Proportional Representation on August 21st?
There are many forms of PR: quotas, state by state,
allowing preferences etc.
Let us suppose that we just a simple national version for the 150
member House of Reps based on 1st preference votes only.
The quota to get any representation could be just the total
number of formal votes divided by 150 seats =
82,683 formal first preference votes.
The CDP makes it over the line, One Nation and
the Country Liberals do not make it.
Say we just ignore the votes that were wasted on the small
parties that did not make this quota. Thus 11,903,018
votes are not wasted and 499,365 votes are wasted.
Now let us divide up the 150 seats amongst the parties
that made it over the quota according to what
proportion of the 11,903,018 votes they got.
The seats in the new parliament [vs current] would be:
ALP 59 seats [actually now 72]
Greens 18 seats [1 seat]
Liberal 48 seats 
LNP(Qld) 14 seats 
Nationals(all states) 6 seats 
Family First 4 seats 
CDP 1 seat 
So we would also probably have an ALP-Green Coalition
government led by PM Gillard, but it would be
Greener, less Indy-ish and hold a slightly
more substantial majority.