We are already experiencing the symptoms of climate change, especially with a hotter and drier climate in southern Australia - the rush to construct desalination plants is an expensive testament to that.

If you try to come to Australia by boat, even if we think you are the best person in the world, even if you are a Nobel Prize winning genius, we will not let you in.

This is a very tough business, politics. It's easy to get resentful or full of bitterness ... (but) I think hatred hurts the hater more than the hated. So I'm looking back on my time positively.

In economics, one of the most important concepts is 'opportunity cost' - the idea that once you spend your money on something, you can't spend it again on something else.

If consulted by friends about marital dramas, I always encourage the singles to marry, the married to stick together, the neglectful and wayward to renew their loving commitment and the wronged to forgive.

Mitt Romney speaking to a $50,000-a-plate Republican fundraiser says he doesn't have to worry about the 47 per cent of Americans who don't pay tax. He was not counting on the smart phone recording his speech and then posting it on YouTube.

You will never find a better friend to the United States than Australia.