World Rugby Rankings are calculated using a ‘Points Exchange’ system, in which sides take points off each other based on the match result.
In other words whatever one side gains, the other loses.
World Rugby rankings: How the system works
The abovementioned exchanges are based on the match result, the relative strength of each team, and the margin of victory, and there is also an allowance for home advantage.
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Points exchanges are doubled during the World Cup Finals to recognise the unique importance of this event, but all other full international matches are treated the same, to be as fair as possible to countries playing a different mix of friendly and competitive matches across the world.
Any match that is not a full international between two member countries does not count at all.
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All member countries have a rating, typically between 0 and 100. The top side in the world will normally have a rating above 90.
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.
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Can you tell in advance of matches what effect results will have on the rankings?
Those involved with matches can know what is at stake in the World Rugby Rankings, going into the match and the exact permutations of score and changes.
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.
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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.
According to World Rugby: “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.”
World Rugby Rankings are updated every Monday and can be viewed here.