Yep, been asked this a few times. Try this post::
https://hotcopper.com.au/threads/banter-and-general-comments.4474625/page-20340?post_id=53192438
If you need something more just ask. There are a lot of valuable explanations in this thread so it is worth spending a few hours going back over the history and reading the posts - we tend to explain as we go along.