However, the International Crisis Group points out that figures from the 1987 census, as well as the 1967, 1977, and 1997 censuses, "are all considered highly problematic, due to suspicions of regime manipulation" because Iraqi citizens were only allowed to indicate belonging to either the Arab or Kurdish ethnic groups; consequently, this skewed the number of other ethnic minorities, such as Iraq's third largest ethnic group – the Turkmens/Turkomans. A report published by the European Parliamentary Research Service suggests that in 2015 there was 24 million Arabs (15 million Shia and 9 million Sunni); 4 million Sunni Kurds (plus 500,000 Shia Faili Kurds and 200,000 Kaka'i); 3 million Iraqi Turkmen/Turkoman; 1 million Black Iraqis; 500,000 Christians (including Chaldean, Syriacs, Assyrians and Armenians); 500,000 Yazidis; 250,000 Shabaks; 50,000 Roma; 3,000 Sabean-Mandaeans; 2,000 Circassians; 1,000 Baha'i; and a few dozen Jews. Around 20,000 Marsh Arabs live in southern Iraq. Iraq has a community of 2,500 Chechens. In southern Iraq, there is a community of Iraqis of African descent, a legacy of the slavery practised in the Islamic Caliphate beginning before the Zanj Rebellion of the 9th century, and Basra's role as a key port. It is the most populous country in the Arabian Plate. The main languages spoken in Iraq are Mesopotamian Arabic and Kurdish, followed by the Iraqi Turkmen/Turkoman dialect of Turkish, and the Neo-Aramaic languages (specifically Chaldean and Assyrian). Arabic and Kurdish are written with versions of the Arabic script. Since 2005, the Turkmen/Turkoman have switched from the Arabic script to the Turkish alphabet. In addition, the Neo-Aramaic languages use the Syriac script. Other smaller minority languages include Mandaic, Shabaki, Armenian, Circassian and Persian. Prior to the invasion in 2003, Arabic was the sole official language. Since the new Constitution of Iraq approved in June 2004, both Arabic and Kurdish are official languages, while Assyrian Neo-Aramaic and the Turkmen/Turkoman dialect of Turkish (referred to as respectively "Syriac" and "Turkmen" in the constitution) are recognised regional languages. In addition, any region or province may declare other languages official if a majority of the population approves in a general referendum.