ratio is roughly balanced, with proportionally about as many men as women. There is little reliable statistical information on urbanization in Somalia. Rough estimates have been made indicating a rate of urbanization of 4.79% per annum (2005–2010 est.), with many towns quickly growing into cities. Many ethnic minorities have also moved from rural areas to urban centres since the onset of the civil war, particularly to Mogadishu and Kismayo. , 37.7% of the nation's population live in towns and cities, with the percentage rapidly increasing. Languages Somali and Arabic are the official languages of Somalia. The Somali language is the mother tongue of the Somali people, the nation's most populous ethnic group. It is a member of the Cushitic branch of the Afro-Asiatic language family, and its nearest relatives are the Oromo, Afar and Saho languages. Somali is the best documented of the Cushitic languages, with academic studies of it dating from before 1900. Somali dialects are divided into three main groups: Northern, Benadir and Maay. Northern Somali (or Northern-Central Somali) forms the basis for Standard Somali. Benadir (also known as Coastal Somali) is spoken on the Benadir coast, from Adale to south of Merca including Mogadishu, as well as in the immediate hinterland. The coastal dialects have additional phonemes that do not exist in Standard Somali. Maay is principally spoken by the Digil and Mirifle (Rahanweyn) clans in the southern areas of Somalia. Benadiri is the main dialect spoken in the country, in contrast to Northern Somali which is the main dialect spoken in Somaliland. A number of writing systems have been used over the years for transcribing the Somali language. Of these, the Somali alphabet is the most widely used, and has been the official writing script in Somalia since the Supreme Revolutionary Council formally introduced it in October 1972. The script was developed by the Somali linguist Shire Jama Ahmed specifically for the Somali language, and uses all letters of the English Latin alphabet except p, v and z. Besides Ahmed's Latin script, other orthographies that have been used for centuries for writing Somali include the long-established Arabic script and Wadaad writing. Indigenous writing systems developed in the 20th century include the Osmanya, Borama and Kaddare scripts, which were invented by Osman Yusuf Kenadid, Sheikh Abdurahman Sheikh Nuur and Hussein Sheikh Ahmed Kaddare, respectively. In addition to Somali, Arabic is an official national language in Somalia. Around