The population of Yemen in 2003 was estimated by the United Nations at 20,010,000, which placed it as number 51 in population among the 193 nations of the world. In that year approximately 3% of the population was over 65 years of age, with another 48% of the population under 15 years of age. There were 103 males for every 100 females in the country in 2003. According to the UN, the annual population growth rate for 2000–2005 is 3.52%, with the projected population for the year 2015 at 30,677,000. The population density in 2002 was 35 per sq km (91 per sq mi). Most of the population is concentrated in the Tihama foothills and central highlands of Yemen. Most of southern Yemen is very sparsely populated.
It was estimated by the Population Reference Bureau that 25% of the population lived in urban areas in 2001. The capital city, Sanaa, had a population of 1,231,000 in that year. Other large cities include Taiz (2,206,000), Hodiedah (1,750,000), and Aden (562,000), the chief port and former capital of the PDRY. According to the United Nations, the urban population growth rate for 2000–2005 was 4.7%.