We have analysed the football results from the top four English leagues and FA Cup going back 16 years, 30 European leagues going back 10 years and all the European competitions, including the Champions League, UEFA Cup, Cup Winners Cup and Intertoto Cup, going back to 1990. This amounts to more than 130,000 games.

We take all the results and use several factors to determine a teams' ranking. The most important factors are the quality of the team's opposition and the result gained. For example, if a Championship side beats Chelsea they will receive more points than by beating another Championship side.

The result gained is also of fundamental importance: a win is better than a draw which is better than a loss, no matter who the opposition. The most recent results receive a heavier ranking than older results, so if Preston North End beat Manchester United last weekend it will have a greater effect on their ranking than the same result four years ago. Getting a result away from home is weighted more heavily than a home result. Finally the more importance of a match also is taken into consideration, for example playing in the Champions League quarter-finals is worth more than a league match but not as much as playing in the final itself.

By analyzing all the available results with reference to our ranking algorithms we can accurately determine the relative strengths of teams, even if they have never played each other.