When I look at the following site it says (at the time of writing) that the total market capitalization of Bitcoin is $125,927,574,809 AUD.
Now I think you could do this by running through the entire history of transactions on the blockchain, adding them all up, and multiplying by the current price. But there is probably a better way.
My question is: What is the method to determine the total market capitalization of the Bitcoin market?