Bangladeshi citizenship was formed in 1971, when the permanent residents of the former East Pakistan were transformed into citizens of a new republic.[31] Bangladesh is the world's eighth most populous nation. The vast majority of Bangladeshis are ethnolingustically Bengalis, an Indo-Aryan people who are predominantly Muslim. The population of Bangladesh is concentrated in the fertile Bengal delta, which has been the center of urban and agrarian civilizations for millennia.