Prior to the beginning of the English Premier League season, Sportify published preseason rankings based on an Elo-style rating model along with insights for each of the teams in England’s top flight.
After Week 1, this is how the Sportify model ranks the 20 teams:
Six teams started the season with a four-position difference from the preseason Sportify Power Rankings: Arsenal (-4); Southampton (-4); Crystal Palace (-4); Bournemouth (-4); West Bromwich Albion (+4); and Hull City (+4). Two, Liverpool and Swansea City, had a three-position difference, both upward moves. Two others, Manchester United and Middlesbrough, had a two position difference, also positive, and eight teams were one position above or below the preseason ranking. Stoke City and Burnley saw no change in position; however, Stoke went from 1529 points to 1534 points with a 1-1 draw at Middlesbrough, and Burnley dropped a dozen points with a 0-1 loss at home to Swansea City.
As of Week 2, the position changes will be marked by arrows in the Change column. Additionally, game details including xG-based insights will be available in our Game Center, which will see a facelift in the coming weeks.
— Manchester United (@ManUtd) August 14, 2016
The method: The Elo rating system
Elo ratings are a calculation of performance in head-to-head competitions originally developed for chess. This method has been used to rate a variety of competitions, including soccer. For each team, the calculation considers final scores, margin of victory, home field advantage and strength of schedule.
Sportify builds on existing ELO methodology, improving the season starting rating by using a combination of a proportion of a team’s rating in the previous season and a proportion of the league’s average rating. Wins always add points and losses always deduct points. Unexpected results, such as the upset of a strong team by a lower rated team, cause a greater fluctuation in points compared to “expected” results.