You're correct, of course, that it's very difficult to get good information due to the nature of smuggling and trafficking. It's one of those things that the harder you look for it, the more you tend to find.
We do in fact have a certain level of overstaying within the country. At present probably about 15,000 to 16,000 people are unlawfully in the country, and we can tell that because of the controls we exercise at entry and exit. Many of those will be people who did intend to overstay and perhaps work unlawfully but who entered often with assistance, often with the help of people who could tell them what to say and provide them with information that would enable them to pass our controls.
With regard to trafficking, as far as we can tell, we do not have high levels; nonetheless, trafficking is obviously a massive concern because the exploitation of human beings that it represents is something that no country wants to be party to.
The major ways we combat both of them are largely internationally through the Bali process and internally through the best compliance processes we can manage. We have strong penalties in our legislation now for people who aid other people to knowingly circumvent our visa controls.
That's probably the general tenor of my comment.