in 1960, 4 billion in 1974, 5 billion in
1988, and 6 billion in 2000. For the 21st century, the continued
exponential growth in science and technology raises both hopes
(e.g., advances in medicine) and fears (e.g., development of even
more lethal weapons of war).

Yemen
North Yemen became independent of the Ottoman Empire in 1918.
The British, who had set up a protectorate area around the southern
port of Aden in the 19th century, withdrew in 1967 from what became
South Yemen. Three years later, the southern government adopted a
Marxist orientation. The massive exodus of hundreds of thousands of
Yemenis from the south to the north contributed to two decades of
hostility between the states. The two countries were formally
unified as the Republic of Yemen in 1990. A southern secessionist
movement in 1994 was quickly subdued. In 2000, Saudi Arabia and
Yemen agreed to a delimitation of their border.

Zambia
The territory of Northern Rhodesia was administered by the
South Africa Company from 1891 until it was taken over by the UK in
1923. During the 1920s and 1930s, advances in mining spurred
development and immigration. The name was changed to Zambia upon
independence in 1964. In the 1980s and 1990s, declining copper
prices and a prolonged drought hurt the economy. Elections in 1991
brought an end to one-party rule, but the subsequent vote in 1996
saw blatant harassment of opposition parties. The election in 2001
was marked by administrative problems with three parties filing a
legal petition challenging the election of ruling party candidate
Levy MWANAWASA. The new president launched a far-reaching
anti-corruption campaign in 2002, which resulted in the prosecution
of former President Frederick CHILUBA and many of his supporters in
late 2003. Opposition parties currently hold a majority of seats in
the National Assembly.

Zimbabwe
The UK annexed Southern Rhodesia from the South Africa
Company in 1923. A 1961 constitution was formulated that favored
whites in power. In 1965 the government unilaterally declared its
independence, but the UK did not recognize the act and demanded more
complete voting rights for the black African majority in the country
(then called Rhodesia). UN sanctions and a guerrilla uprising
finally led to free elections in 1979 and independence (as Zimbabwe)
in 1980. Robert MUGABE, the nation's first prime minister, has been