The general entrance requirement for university is Abitur, a qualification normally based on continuous assessment during the last few years at school and final examinations; however there are a number of exceptions, and precise requirements vary, depending on the state, the university and the subject. Germany's universities are recognised internationally; in the Academic Ranking of World Universities (ARWU) for 2008, six of the top 100 universities in the world are in Germany, and 18 of the top 200. Nearly all German universities are public institutions, tuition fees in the range of €500 were introduced in some states after 2006, but quickly abolished again until 2014.