The Shia (/ˈʃiːə/; Arabic: شيعة Shīʿah) represent the second largest denomination of Islam. Adherents of Shia Islam are called Shias or the Shi'a as a collective or Shi'i individually. Shi'a is the short form of the historic phrase Shīʻatu ʻAlī (شيعة علي) meaning "followers", "faction" or "party" of Muhammad's son-in-law and cousin Ali ibn Abi Talib, whom the Shia believe to be Muhammad's successor in the Caliphate. Twelver Shia (Ithnā'ashariyyah) is the largest branch of Shia Islam, and the term Shia Muslim is often taken to refer to Twelvers by default. As of 2009[update] Shia Muslims constituted 10-13% of the world's Muslim population, Shias comprised 11-14% of the Muslim population in the Middle East-North Africa region, and between 68% and 80% of Shias lived in four countries: Iran, Pakistan, India and Iraq. Shia Islam is based on the Quran and the message of the Islamic prophet Muhammad attested in hadith recorded by the Shia, and certain books deemed sacred to the Shia (Nahj al-Balagha).