Iran with a population of over 77 million is the leading Shiite Muslim state. Despite its oil Iran, partly as a result of Western sanctions, remains relatively poor with an annual GDP per person of under $5,000.
Saudi Arabia with a population of just under 30 million is predominantly Sunni. It is a wealthy country because of its huge oil reserves. Its annual GDP per person is over five times that of Iran. It includes within its borders the holy places of Mecca and Medina.
There are many more Sunni adherents than there are Shiites in the world today. Sunnis include many different types of believers such as proponents of puritanical Wahhabism and Sufism, which developed in Saudi Arabia. Both Sunnis and Shiites have varying attitudes to the modern world. Some are ascetics and some intolerant extremists with a medieval mindset, but there are moderate Sunnis and Shiites who support democratic ways and institutions,