Cost of compulsory third party insurance

I received my car rego renewance letter yesterday and it came with a flyer explaining how the compulsory third party insurance included in the rego price worked. At the end of this flyer they also presented the comparative costs of the premium between the different states. Got onto their website and here it is:

PREMIUMS AUSTRALIA WIDE
The table below shows a State by State comparison of compulsory third party insurance premiums for private motor cars (exc. GST).
State As at July 2005
Northern Territory $388
Australian Capital Territory $351
Victoria $347
South Australia $341
Tasmania $302
New South Wales $296*
Queensland $276*
Western Australia $228

* For Queensland and New South Wales, lowest premium on offer amongst private insurers is shown.

It seems that WA is very attractive to register a vehicle. I am not sure what the remaining cost of my rego is though so it would be hard to compare the total cost of the rego with other states but for the CTP part WA is good.

Anyone knows why there would be such a difference between states (different road regulations, i.e. no speed limit in NT open roads, accident statistics,...????)

cheers,
SLY.