How world rankings are calculated, and what they miss
World rankings are a published formula applied to a defined set of international matches, updated at set windows rather than after every game.
A world ranking is not a table of who is playing well this month. It is a formula applied to results in recognised international matches and published by the governing body of the sport. Rugby union and football both publish enough detail to show how the machinery works, and why a ranking can shift without a team kicking a ball.
A points exchange, not a league table
World Rugby calculates its men's and women's rankings with a points exchange system. Sides gain or lose points based on the result, with the relative strength of each team, the margin of victory and an allowance for home advantage all feeding into the calculation. Every member union has a rating, typically between 0 and 100, and the top side in the world will normally sit above 90. Because it is an exchange, one team's gain is another team's loss: beating a higher-rated opponent moves you further than beating a lower-rated one.
Only some matches count
Not every game between two countries counts. World Rugby states that a match must be a full international between two member unions or it does not count at all, and that all such matches are treated the same whether they are friendlies or competitive fixtures. Points are doubled during the World Cup Finals to reflect the importance of the tournament. Football applies a comparable filter in a different way: FIFA notes that if a match is downgraded below A-international status after it has been played, the points from it will not be counted in the next official update.
Updates arrive in windows
Rankings become official at fixed points rather than the moment a match ends. FIFA publishes a next official update date, and notes that matches played outside official international match windows are not reflected until the end of the following ranking window. Where full coverage is not available for a match, live rankings are updated only at full time, so a provisional figure can change minutes later.
What a ranking does not tell you
A ranking measures results against a formula, nothing more. It does not account for injuries, travel, squad changes or the conditions a match was played in, and it is not a prediction. Its practical jobs are seeding, qualifying paths and grouping teams of similar standard, which is why the method is published openly. The calculation pages at world.rugby and inside.fifa.com show the current ratings and the update schedule.
The bottom line: a world ranking is a published formula applied to a defined set of internationals and updated at set windows. Read it as a record of results, not as a verdict on how good a team looks.