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Wednesday, February 15, 2012
SPI vs. FIFA World Ranking


With today's monthly release of the FIFA World Rankings, let's again look at how that system differs from ESPN's Soccer Power Index.

Full SPI methodology can be found here and here, but the short version is that SPI is a predictive, forward-looking rating system, while FIFA's rankings are reactionary. With that in mind, here is how both fared and reacted over the past month, focusing on the Africa Cup of Nations, the only significant international action in that time.

• SPI correctly projected five of the eight Cup of Nations quarterfinalists, including three group winners. FIFA's rankings predicted four of eight quarterfinalists and two group winners. Overall, SPI's pre-tournament rankings prognosticated significantly better, with a correlation of 0.39 to FIFA's 0.28 (on a scale of minus-1 to plus-1).

• While neither system saw eventual champion Zambia reaching the quarters, SPI did rate Zambia a narrow third favorite in Group A, which was considered the weakest and most even group. SPI put Zambia's 48.6 percent chances of advancing only four percentage points behind Libya. Senegal was the group favorite at 69.7 percent to advance.

• On the strength of its first championship, Zambia moved up 17 spots to 60th in SPI, the only country to rise more than seven places. After losing all three matches, Senegal (down eight) and Burkina Faso (down seven) were the biggest losers and the only countries to drop more than five spots. The relatively small amount of movement is indicative of SPI's predictive nature.

• Contrast this with FIFA's rankings, in which nine of the 16 countries made double-digit moves, led by huge rises for co-hosts Gabon (up 46 to 45th) and Equatorial Guinea (up 41 to 110). In SPI, Equatorial Guinea inched up two spots, and Gabon only rose one spot. This is because SPI factors home-field advantage into major tournaments, which meant that the quarterfinal runs by the co-hosts were not nearly as surprising. This is also the reason SPI correctly projected Gabon as Group C winner, while FIFA ranked the Panthers third, behind Tunisia and Morocco.

• Looking at the top of the FIFA rankings, Spain unsurprisingly remains in the first slot. But the reigning world and European champion is second in SPI, trailing Germany by a small margin. As mentioned previously, this is largely because of Germany's greater dominance on the scoreboard in Euro 2012 qualifying, as well as the 2010 World Cup. Germany outscored opponents by 2.7 goals per game in Euro qualifying, compared to 2.5 goals per game for Spain. In South Africa, Germany posted a plus-11 goal difference, including a combined plus-7 against England and Argentina. Spain, of course, won the title, but a plus-7 goal difference and a quartet of 1-0 wins in the knockout stage did little to help Spain's SPI rating.