Lucky Sevens: The Rugby World Cup

The Rugby World Cup is being held in France right now. Unfortunately, Australia was knocked out by the English Saturday night. The USA didn't make it out of their pool, surprise, surprise. Word is they have a talented pool of young players ready to develop in the next ten years. I'll believe it when I see it. Later Saturday, New Zealand was also dismissed from the comp in their loss to host nation France. These two huge upsets leaves the door wide open for South Africa, looking for their second title.
Your Lucky Sevens question for the month: How many Rugby World Cup titles has Australia won?