A subtle shift in thinking
The aim of any betting ratings' system is not to predict the future, but to predict the likelihood of a range of possible outcomes based on available information.
This subtle distinction usually marks the difference in the way that losing and winning punters think: the former assumes that the future is already written, and that it is their job to divine it; the latter recognises that divination is impossible, but that they can assign probabilities to a range of possible futures, and place bets accordingly.
With this subtle shift in thinking comes a shift in language. "France," no longer, "are going to win the Six Nations". Instead, "France have a 29% chance of winning the Six Nations, so should be around 3.505/2".
These shifts in thinking and language lead to a shift in behaviour: betting becomes the act of only backing those outcomes whose chance of happening is greater than their odds imply.
But how to make the shift?
Fine, but assessing the percentage chance of possible outcomes is not easy.
To help in this, most profitable punters use a ratings' system, a statistical method that assigns values to previous matches and uses those values to compare the chances of teams in future.
Doing this in international rugby is difficult, though.
Most of my betting these days is on men's tennis, a sport with thousands of matches played by the same competitors season-after-season. International rugby, by comparison, has few matches, and teams and their set-ups can often change significantly from match-to-match and year-to-year. The dataset is less rich, more variable, and therefore less-reliable.
However, this does bring some advantages. Whereas the betting markets in tennis are highly competitive, with thousands of data-savvy punters vying over increasingly smaller margins, the same is not true in international rugby, where markets still seem dominated by media bias and tribal thinking.
As a would-be profitable rugby punter, then, it might be harder to arrive at a perfect ratings' system, but getting anywhere close will still give you a huge advantage over the market.
Picking the right ratings
Just make sure you pick the right ratings.
Rugby fans will be familiar with World Rugby's rankings and might assume that they offer a useful statistical insight into the chances of the nations who will contest the Six Nations that begin on Saturday 5th February.
If they did, they would see England as the likely winners, ahead of Ireland and France, with the other teams languishing below that.
Thinking like this would be a mistake.
World Rugby's rankings serve a purpose in helping promote the game. They offer a marketable who's-up-and-who's-down that can be pushed to media outlets, and latched onto by fans as a snapshot of what's what. In this way they are no-doubt successful.
They are unlikely, though, to help punters who want an insight into the chances of those teams contesting the Six Nations. World Rugby's rankings consider a range of factors - winning margin, relative opponent strength, home advantage, importance of match, and the list goes on - that are either irrelevant, statistically misunderstood, arbitrarily employed, or mis-applied for that purpose.
This isn't me beating-up on World Rugby. They don't advertise their ratings as a tool to inform betting. It is, though, a warning to punters not to assume that those rankings will help to make more profitable betting decisions.
Bring on the Elo ratings
Several years ago - when writing some pieces about the approaches used by varying sporting bodies to rank their competitors - I used a tried-and-tested predictive tool - Elo ratings - to compare the value of other approaches. Although not a regular rugby punter, I still update them before major tournaments, and despite the statistical drawbacks of the game as mentioned above, they remain surprisingly profitable.
And this year's Six Nations?
Those ratings rank the teams as follows:
2346 - Ireland
2301 - England
2240 - France
2182 - Scotland
2178 - Wales
1615 - Italy
To set these ratings in context, the approximate 100-point lead Ireland have over France would suggest that - at a neutral ground - they would have around a 65% chance of winning, or be 1.538/15 to France's 2.8615/8.
If wanting a belt-and-braces approach to the tournament, I would usually create a Monte Carlo analysis - a statistical tool that plugs these ratings into a programme that churns out thousands of simulated Six Nations - allowing me to arrive at a more accurate tissue price for the tournament.
Sometimes, though, such work is unnecessary.
The briefest of looks at the market show that Ireland, third-favourites at (4.2016/5), are the obvious value bet. They may well face France (2.6413/8) and England (3.953/1) away, but even adjusting for that disadvantage, Ireland are the team to beat.