Hi dopey, Your graph shows Australian Government debt up to 2008 which, given what has happened in the interim, is about as good as tits on a bull.
The Australian Debt Clock* (there's no other comprehensive up to date Australian Debt info available on one site that I can find) indicates that our Commonwealth, State & Municipal debt is about $630 billion and our GDP is about $1,58 trillion which would make a combined government debt of about 40% or $27K per man, woman and child.
If one assumes that during this government's term of office that Commonwealth debt will hit the new $500 billion ceiling and that State & Municipal debt will go up proportionately then we could be faced by a combined government debt of $926 Billion of combined government debt or about 58% of GDP.
If you have more Authorative and up to date info, I'd really appreciate it.