IRB World Rankings Preview Available Tuesday

  
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11/6/2012
By IRB Media Unit


As the countdown to the Rugby World Cup 2015 Pool Allocation Draw continues, the spotlight will be firmly on the end of year internationals to see whether teams are able to improve their banding for the event on December 3.

The IRB will issue a rankings preview for this weekend's matches on Tuesday (tomorrow). This will be supplemented on Thursday with dedicated previews and head to heads for the majority of the Tier 1 and Tier 2 November Tests. A rankings update will be issued at 12 midday(UK time) every Monday outlining the amendments to the rankings following the previous weekend's matches.

If the draw happened today

As was the case for the RWC 2011 draw, the 2015 draw will include the 12 directly qualified teams (the top three teams in each RWC 2011 pool). Those teams will be split into three bands according to their position in the IRB World Rankings as of 12 midday (UK time) on December 3.

If the draw happened today (November 5) the three bands would be as follows:
Band 1: New Zealand, Australia, South Africa, England (currently 1-4 in IRB World Rankings)
Band 2: France, Wales, Ireland, Argentina (currently 5-8 in IRB World Rankings)
Band 3: Scotland, Samoa, Italy, Tonga (remaining four automatically qualified teams in order of rankings position)

The eight qualifying places will be allocated into the other two bands as follows:
Band 4: Oceania 1, Europe 1, Asia 1, Americas 1
Band 5: Africa 1, Europe 2, Americas 2, Repechage winner

Predicting the rankings

In order to accurately rank a single team against all the other teams in the IRB World Rankings, the system must take into account all matches for all teams. This is one of the key strengths of the system.

In terms of predicting future rankings, this is quite straightforward when there are one or two matches to take into consideration, but as the number of matches grows, so the variables to consider mushroom.

On October 27, 2012, for example, there were seven international matches that counted towards the IRB World Rankings. With two teams each having five possible outcomes for each match (win, win by more than 15, lose, lose by more than 15, draw), there were 10 million potential outcomes as far as the rankings is concerned!

In the end, these seven matches caused 39 positional changes in the rankings.

There are scheduled to be 38 matches between November 9 and December 1, 2012 that will count towards the IRB World Rankings with 1036 possible permutations.

This means that, realistically, the impact on the rankings can only be predicted for one round of matches at a time. The impact of future results cannot predicted until the week of those matches.

MORE ON THE IRB WORLD RANKINGS HERE

The IRB World Rankings are calculated using a 'Points Exchange' system, in which sides take points off each other based on the match result. Whatever one side gains, the other loses.

The exchanges are based on the match result, the relative strength of each team, and the margin of victory, and there is an allowance for home advantage.

Any match that is not a full international between two full IRB Member Unions does not count at all. For example, the result of the match between Ireland XV and Fiji in Limerick on November 17 does not affect the rankings.

Frequently Asked Questions

Q. Can you tell in advance of matches what effect results will have on the rankings?
Yes we can, and this means that those involved with matches can know what is at stake, going into the match.
For each match, there are only five possible outcomes that can affect points exchanges: either side winning by more than 15 points, either side winning by up to 15 points, or a draw. In each case, we can advise how many rating points each side will gain or lose. This type of preview information may be posted on the site.

Q. Does the system produce accurate and reliable rankings?
Several years' research went into developing the system, using an extensive database of international matches going back to 1871. All the weightings and values in the system were derived from detailed analysis of the results.
The system's reliability is assessed in a number of objective ways, including measuring its 'Predictive Accuracy'. If, over a period of time, the system tends to be good at predicting which side will win each match, then we can be confident that it is presenting an accurate and reliable picture of current strength, and responding appropriately to changes in form.

Q. How do you allow for home advantage?
When calculating points exchanges, the home side is treated as though they are three rating points better than their current rating. This has the effect of 'handicapping' the home side as they will tend to pick up fewer points for winning and give away more points for losing. In this way, the advantage of playing at home is cancelled out.

Q. How important is 'margin of victory' under the system?
The research suggested that match results are more important than margins of victory in producing accurate rankings. For instance, whether a side wins by 60 points or 100 points against much lower-rated opposition is not a good indicator of future performance. However, the analysis also indicated that it is significant whether sides win relatively comfortably - with 'something to spare' - so a weighting is applied where a side wins a match by more than 15 points.

Q. Do sides earn credit for losing narrowly to higher rated opponents?
No they don't. In this system, you can't win points for losing, or lose points for winning. While it may be attractive to award points for heroic defeats, it is less appealing to deduct points from a team that has won. If the close match was an indication of a genuine shift in relative strength, this would be reflected in other results.

Q. Will some countries tend to be higher rated at certain times of the year, such as following the 6 Nations or Rugby Championship?
No. As all matches are worth a total of 0 points (as whatever one side gains, the other loses) there is no particular advantage to playing more matches. Under the system, a country has a certain rating, which stays the same until they play again. Although matches often result in points exchanges, relatively 'predictable' results lead to very minor changes, and may result in no change to either side's rating at all.

Q. How important are past achievements in calculating the rankings?
The system is designed to produce an accurate picture of current strength, based on results. The importance of past successes will fade and be replaced by more recent results.

Q. How does the system deal with freak results?
There is a maximum that any side's rating can move, either up or down, based on one match result, to make sure that the system does not over-react.