The Dutch Football Fan Map is based on data supplied by every professional football club in the Netherlands. Each of the 34 clubs of the Eredivisie and the Jupiler League were asked to supply information as to the number of season ticket holders and where they live. The data applied to season 2013-2014 and the clubs ensured the identities of their fans remained anonymous.
The information for the colourful map was taken from World Ticketing System (WTS) with the help of KNVB Expertise, a research organization with close links to the Dutch football’s governing body, the KNVB. The data is accurate up to September 2014. The WTS register all season tickets sales in the land.
There is no data available for Jong Ajax, Jong PSV, Jong FC Twente and Achilles'29, because they are participating in the Jupiler League as amateur clubs. These clubs are not affiliated to the WTS so their season ticket holders are not registered by them. To colour the map only season ticket data from individuals or company holders has been used. A small number of season ticket holders are not included in the fan map. These include supporters from abroad and season ticket holders who have a Post Office box address.
The map is mostly colored using recognizable club colors. To keep the map organized some small deviations have been made. The color intensity is determined by the number of season ticket holders per town, district, village. As well as postcode.
Data from the Dutch Central Bureau of Statistics is used to determine the population of each postcode . The more season ticket holders a club has per 100 inhabitants , the brighter the color. Three levels of intensity are used . Postcodes where no season ticket holders attend are left white . In the overview 'All Clubs ' postcodes are colored to the club with the most season ticket holders in that area.
The map is made following the lead by the Swiss Tages Anzeiger.