abat's
sovereignty ended in a 1991 UN-brokered cease-fire; a UN-organized
referendum on final status has been repeatedly postponed.

World
Globally, the 20th century was marked by: (a) two devastating
world wars; (b) the Great Depression of the 1930s; (c) the end of
vast colonial empires; (d) rapid advances in science and technology,
from the first airplane flight at Kitty Hawk, North Carolina (US) to
the landing on the moon; (e) the Cold War between the Western
alliance and the Warsaw Pact nations; (f) a sharp rise in living
standards in North America, Europe, and Japan; (g) increased
concerns about the environment, including loss of forests, shortages
of energy and water, the decline in biological diversity, and air
pollution; (h) the onset of the AIDS epidemic; and (i) the ultimate
emergence of the US as the only world superpower. The planet's
population continues to explode: from 1 billion in 1820, to 2
billion in 1930, 3 billion 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