I am wondering how the bookmakers calculate the odds about football matches. There is no chance that they do that on hand, because the games are simply too much. So there must be some sort of mathematical algorithm. Therefore, having in mind that bookmakers have all the football statistics, how do they do it? I have recently come across a very interesting website called

Футболът е математика, футболни прогнози за всеки кръг чрез алгоритъм. , which gives football predictions based on mathematical statistics. Unfortunately, they did not reveal me their algorithm. So, can anyone help me ?