En regardant le lien donné par 11G sur le topic CDM2010, je suis tombé sur cette étude :
Citation
The fans are undoubtedly the true and principal asset of any football club. They are the largest power generating revenue, directly or indirectly, without which no club can grow, whether sports or financially. A recent study released by a Brazilian magazine, showed the number of supporters of the biggest clubs in the world. The study was based on research conducted in 11 countries, on the football authorities, or by statistical offices. The data presented also show the% that the number of adherents to the population of each country according to population projections from the U.S. Census Bureau 2008.
Note: these studies were not considered the number of supporters of each club out of their country of origin.
BRAZIL - Search Datafolha, 2007
1. Flamengo - 32.6 million (17%)
2. Corinthians - 23 million (13%)
3. Sao Paulo - 15.3 million (8%)
ARGENTINA - Equis Social Research, 2006
1. Boca Juniors - 16.4 million (40.4%)
2. River Plate - 13.2 million (32.6%)
3. Independiente - 2.2 million (5.5%)
SPAIN -- Center for Sociological Research, 2007
1. Real Madrid - 13.2 million (32.7%)
2. Barcelona - 10.4 million (25.7%)
3. Valencia - 2.1 million (5.3%)
GERMANY -- Sportfive (Sports Marketing Agency), 2007
1. Bayern Munich - 10.5 million (12.8%)
2. Werder Bremen - 5.7 million (6.9%)
3. Schalke 04 - 4.3 million (5.2%)
ITALY - I NSTITUTE Demos-Eurisko, 2007
1. Juventus - 16.3 million (28%)
2. Milan - 13.4 million (23%)
3. Internazionale - 9.3 million (16%)
JAPAN -- Video Research Ltd., 2006
1. Kashima Antlers - 12.3 million (9.7%)
2. Gamba Osaka - 11.9 million (9.4%)
3. Jubilo Iwata - 11.7 million (9.2%)
MEXICO -- Grupo Reforma, 2007
1. Chivas - 30.8 million (28%)
2. America - 26.4 million (24%)
3. Cruz Azul and Pumas - 13.2 million (12%)
ENGLAND -- Roy Morgan International, 2006
1. Manchester United - 4.2 million (6.9%)
2. Liverpool - 3.1 million (5.1%)
3. Arsenal - 2.6 million (4.35%)
PORTUGAL -- Portuguese League for Professional Football, 2003
1. Benfica - 4.1 million (38.8%)
2. Porto - 2.6 million (24.4%)
3. Sporting - 2.1 million (20.2%)
FRANCE -- Institut National de la Statistique et des Etudes Economiques (INSEE), 2006
1. Olympique Marseille-10.2 million (16%)
2. Lyon - 9.6 million (15%)
3. Paris Saint-Germain - 3.2 million (5%)
NETHERLANDS -- TNS-NIPO, 2007
1. Ajax - 4.3 million (26%)
2. Feyenoord - 3.8 million (23%)
3. PSV - 2.1 million (13%)
Autant ça me semble correspondre avec la réalité "du terrain" sur la plupart des pays (même si je ne voyais pas le Milan devant l'Inter, et le Bétis devant Valence en Espagne), autant concernant la France, c'est
Lyon, 9.6 M de "supps" (sympathisants) déclarés ? Ce sont les sondages mickey-parade ?

(bon c'est l'INSEE ok, remarquez on est pas loin dans la forme...)