Since the beginning of this century, the population of Iran has increased at a very rapid rate. In 1875, it was estimated at six million people; in 1956, the first official census recorded over 18 million. At the time of the 1976 census this figure had grown to 49.4 million people. The 1992 census determined it totalled just under 60 million, with a density of 35 people per square kilometre. The present population is estimated to be 77 million, and is expected to double within the next thirty years.
One of the main features of the population distribution in Iran during the second half of the XX century has been the rural exodus towards the large urban centres, particularly Tehran, Mashhad, Tabriz and Shiraz. This movement, at its strongest during the 1960s and '70s, has now slowed down somewhat although it is still noticeable. During Rafsanjani's presidency (1989-97), 400,000 jobs were created in one year; now 800,000 new jobs are needed each year just to keep pace.
The numerous migrations of peoples who have passed through Iran, sometimes settling there, have created an ethnically diverse population. The biggest influence has come from Central Asia, first the Indo-European tribes that arrived on the plateau in the II and I millennia ВС. Small communities of Jews and Greeks settled in Iran as mercenaries, traders, doctors etc, which had little impact until the invasion of Alexander, whilst the Arab invasions on the mid VII century massively restrcutured the whole region. Arab garrison towns were founded; Arab nomad pasloralists occupied large tracts of land; the Iranian nobility were dispossessed and only found a toe-hold in the new dispensation as clients of Arab patrons; and descendants of the Arab Prophet (Seyyed descendants of the Imams) became the new hereditary elite of the Islamic cities of Iran. Intermarriage and the cultural prestige of the defeated Sassanian empire led to the adoption of the Persian language by most of these settlers. The same held true for the Turkish and Mongol tribes, who migrated to Iran between the X and XIV centuries AD, though the considerably greater numbers involved led to the turkicisation of considerable areas of Azerbaijan and Khorasan, and a genreralised bi-lingualism.
Traditionally, there has always existed a close link in Iran between the ruling dynasty and the domination of one particular tribe or ethnic group (Seljuk, Zand, Qajar). In the XX century, some governments have attempted to carry out national integration of this heterogenous population, in the hope that tribal and cultural distinctions would disappear with the economic and political development of the country. Under Reza Shah in particular, the Persianisation of the population was carried out by vigorous methods, including a policy of enforced settlement of the nomadic tribes. Today, cultural pluralism is officially admitted but the changes that have occurred since the beginning of the century are in most cases irreversible. The traditional way of life of the nomad groups has been drastically altered by their settlement in villages and by the agricultural reforms of 1962, which were accompanied by land redistribution. Traditional pastures are shrinking under pressure from agriculturalists and large-scale nomadism was reduced by the sealing of the political frontiers with the former USSR in the north-east.
The main ethnic minorities live in the mountain regions along the edge of the central plateau; several provinces, such as Baluchestan and Kurdistan, take their names from the dominant group living in them. There are no precise or recent official figures concerning ethnic minorities; however, Iranian minorities (groups speaking Iranian languages other than Farsi, i.e. Kurds, Baluch, and speakers of Caspian dialects such as Gilaki) are estimated at about 30 per cent of the total population of the country and Turkish-speaking groups at 25 per cent. About 1.5 million Arabic-speakers live in Khuzestan on the borders of Iraq.