At a glance: Key info on Egypt, Tunisia, Algeria and Yemen

(CNN) -- Thousands of people clashed with security forces in Egypt on Friday. Those demonstrations followed unrest in the nearby countries of Algeria, Tunisia and Yemen. Here's a look at key information about each of the countries, from CNN research and the CIA World Factbook:

EGYPT

Population: 80,471,869 (July 2010 est.)

Per Capita GDP: $6,200 (2010 est.)

Unemployment: 9.7% (2010 est.)

President Hosni Mubarak has been in power since 1981. He assumed the presidency October 6, 1981 following the assassination of Anwar Sadat. He was re-elected four times - 1987, 1993, 1999 and 2005

ALGERIA

Population: 34,586,184 (July 2010 est.)

Per Capita GDP: $7,400 (2010 est.)

Unemployment: 9.9% (2010 est.)

President Abdelaziz Bouteflika has been in power since April 28, 1999. (Note: The president is both the chief of state and head of government. A November 2008 constitutional amendment separated the position of head of government from that of the prime minister)

TUNISIA

Population: 10,589,025 (July 2010 est.)

Per Capita GDP: $9,500 (2010 est.)

Unemployment: 14% (2010 est.)

Prime Minister Mohamed Ghannouchi took over for President Zine El-Abidine Ben Ali on January 14 after three weeks of violent protests over rising unemployment rates, poverty levels, inflation and government repression forced Ben Ali to flee for Saudi Arabia. He had been in power since November 7, 1987.

Speaker of Parliament Fouad Mebazza was sworn in as interim president on January 15. Mebazza asked Ghannouchi to form a national unity government.

Ministers for the interim government resigned from the ruling party (Constitutional Democratic Rally) on January 20. Both the president and prime minister also resigned.

YEMEN

Population: 23,495,361 (July 2010 est.)

Per Capita GDP: $2,600 (2010 est.)

Unemployment: 35% (2003 est.)

President Ali Abdallah Salih has been in power since May 22, 1990. The former president of North Yemen assumed office upon the merger of North and South Yemen.

Vice President Maj. Gen. Abd al-Rab Mansur al-Hadi has been in office since October 3, 1994. Prime Minister Ali Muhammad Mujawwar has been in office since March 31, 2007