An estimated 99.7% of the Afghan population is Muslim and most are thought to adhere to the Sunni Hanafi school. According to Pew Research Center, as much as 90% are of the Sunni denomination, 7% Shia and 3% non-denominational. The CIA Factbook variously estimates up to 89.7% Sunni or up to 15% Shia. Dr Michael Izady estimated 70% of the population to be followers of Sunni Islam, 25% Imami Shia Islam, 4.5% Ismaili Shia Islam, and 0.5% other religions.