Helen is the 38th most powerful woman in the world?

According to Forbes, New Zealand Prime Minister Helen Clark is the 38th most powerful woman in the world. How can this be? Sure she has been in power for a while, but it seems that she will be retiring next year and handing the reigns to John Key. Surly the position as PM of NZ is powerful, but NZ is not powerful militarily, doesn't really pull too many strings in the UN and is no real threat to anyone. NZ is great a peace keeping some would be inclined to say, but with all due respect, why is Helen Clark in this list? Good on Forbes to think of her, but how do they back it up?