Today I attended the funeral of Peter Hall, one of the finest mathematical statisticians ever to walk the earth and easily the best from Australia. One of the most remarkable things about Peter was his astonishing productivity, with over 600 papers. As I sat in the audience I realised that many of the people there were probably coauthors of papers with Peter, and I wondered how many statisticians in the world would have been his coauthors or second-degree co-authors.

In mathematics, people calculate Erdős numbers — the “collaborative distance” between Paul Erdős and another person, as measured by authorship of mathematical papers. An Erdős number of 1 means you wrote a paper with Erdős; an Erdős number of 2 means you wrote a paper with someone who has an Erdős number of 1; and so on. My Erdős number is 3, measured in two different ways:

- via Peter Brockwell / Kai-Lai Chung / Paul Erdös
- via J. Keith Ord / Peter C Fishburn / Paul Erdös

It seems appropriate that we should compute Hall numbers in statistics. Mine is 1, as I was lucky enough to have coauthored two papers with Peter Hall. You can compute your own Hall number here. Just put your own surname in the second author field.