t - current issues:

air pollution resulting in acid rain in both the US and Canada; the
US is the largest single emitter of carbon dioxide from the burning
of fossil fuels; water pollution from runoff of pesticides and
fertilizers; limited natural fresh water resources in much of the
western part of the country require careful management;
desertification

Environment - international agreements:

party to: Air Pollution, Air Pollution-Nitrogen Oxides,
Antarctic-Environmental Protocol, Antarctic-Marine Living Resources,
Antarctic Seals, Antarctic Treaty, Climate Change, Desertification,
Endangered Species, Environmental Modification, Marine Dumping,
Marine Life Conservation, Ozone Layer Protection, Ship Pollution,
Tropical Timber 83, Tropical Timber 94, Wetlands, Whaling
signed, but not ratified: Air Pollution-Persistent Organic
Pollutants, Air Pollution-Volatile Organic Compounds, Biodiversity,
Climate Change-Kyoto Protocol, Hazardous Wastes

Geography - note:

world's third-largest country by size (after Russia and Canada) and
by population (after China and India); Mt. McKinley is highest point
in North America and Death Valley the lowest point on the continent

People
United States

Population:

303,824,640 (July 2008 est.)

Age structure:

0-14 years: 20.1% (male 31,257,108/female 29,889,645)
15-64 years: 67.1% (male 101,825,901/female 102,161,823)
65 years and over: 12.7% (male 16,263,255/female 22,426,914) (2008
est.)

Median age:

total: 36.7 years
male: 35.4 years
female: 38.1 years (2008 est.)

Population growth rate:

0.883% (2008 est.)

Birth rate:

14.18 births/1,000 population (2008 est.)

Death rate:

8.27 deaths/1,000 population (2008 est.)

Net migration rate:

2.92 migrant(s)/1,000 population (2008 est.)

Sex ratio:

at birth: 1.05 male(s)/female
under 15 years: 1.05 male(s)/female
15-64 years: 1 male(s)/female
65 years and over: 0.72 male(s)/female
total population: 0.97 male(s)/female (2008 est.)

Infant mortality rate:

total: 6.3 deaths/1,000 live births
male: 6.95 deaths/1,000 live births
female: 5.62 deaths/1,000 live births (2008 est.)

Life expectancy at birth:

total population: 78.14 years
male: 75.29 years
female: 81.13 years (2008 est.)

Total fertility rate:

2.1 children born/woman (2008 est.)

HIV/AIDS - adult prevalence rate:

0.6% (2003 est.)

HIV/AIDS - people living with HIV/AIDS:

950,000 (2003 e