Another criterion to count religious populations in Russia is that of "religious observance". Based on this principle, very few Russians would be religious. It has been found that between 0.5% and 2% of people in big cities attend Easter services, and overall just between 2% and 10% of the total population (3 to 15 million people) are actively practising Orthodox Christians. The proportion of practising Muslims among ethnic groups which are historically Islamic is larger, 10% to 40% depending on the group, and yet smaller than any assumption based on the ethnic principle.