Even if a small percentage of imams who certify products as being halal are passing the profits on to terrorist organizations, it potentially represents a large amount of money. Malaysian studies have valued the worldwide halal food industry as between $600 billion to $2.1 trillion. Halal certifications are usually paid by food companies at set annual rates. Considering all the firms worldwide that pay such fees to imam halal certifiers, this amounts to hundreds of millions of dollars. Some halal certifiers have become quite wealthy from the halal certification scheme. Halal certifiers have also been quite secretive about who receives donations, with some admitting only that the funds go to Islamic madrassa schools and mosques. However, many of these madrassas and mosques are linked to the Wahhabis.