How does Google custom its results to country specific result?

[irldonalb]

I wish I could figure out when Google decides to show local results and international results. In Australia I get the following results from google.com.au with “the web” option selected.

Loans: 10 Aus Websites
Home loans: 10 Aus Websites
Interest Free Home loans: 2 Aus Websites

Is it in Google’s opinion that the Australian websites are not targeted enough for “Interest Free Home loans”? There are 1.6 million results from Aus.

Any ideas or thoughts?