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The United States of America is a constitutional federal republic comprising fifty states and a federal district, as well as several territories, or insular areas, scattered around the Caribbean and Pacific. The country is situated mostly in central North America, where its forty-eight contiguous states and Washington, D.C., the capital district, lie between the Pacific and Atlantic Oceans, bordered by Canada to the north and Mexico to the south. The state of Alaska is in the northwest of the continent, with Canada to its east and Russia to the west across the Bering Strait, and the state of Hawaii is an archipelago in the mid-Pacific.

At 3.79 million square miles (9.83 million km˛) and with more than 300 million people, the United States is the third or fourth largest country by total area, and third largest by land area and by population. The United States is one of the world's most ethnically diverse nations, the product of large-scale immigration from many countries.^[1] The U.S. economy is the largest national economy in the world, with a nominal 2006 gross domestic product (GDP) of more than US$13 trillion (over 19% of the world total based on purchasing power parity).^[2][3]

The nation was founded by thirteen colonies of Great Britain located along the Atlantic seaboard. Proclaiming themselves "states," they issued the Declaration of Independence on July 4, 1776. The rebellious states defeated Great Britain in the American Revolutionary War, the first successful colonial war of independence.^[4] A federal convention adopted the current United States Constitution on September 17, 1787; its ratification the following year made the states part of a single republic. The Bill of Rights, comprising ten constitutional amendments, was ratified in 1791.

In the nineteenth century, the United States acquired land from France, Spain, the United Kingdom, Mexico, and Russia, and annexed the Republic of Texas and the Republic of Hawaii. Disputes between the agrarian South and industrial North over states' rights and the expansion of the institution of slavery provoked the American Civil War of the 1860s. The North's victory prevented a permanent split of the country and led to the end of slavery in the United States. The Spanish-American War and World War I confirmed the nation's status as a military power. In 1945, the United States emerged from World War II as the first country with nuclear weapons, a permanent member of the United Nations Security Council, and a founding member of NATO. In the post?Cold War era, the United States is the only remaining superpower?accounting for approximately 50% of global military spending?and the dominant economic, political, and cultural force in the world.^[5]

Etymology

The term America, for the lands of the western hemisphere, was coined in 1507 after Amerigo Vespucci, an Italian explorer and cartographer.^[6] The full name of the country was first used officially in the Declaration of Independence, which was the "unanimous Declaration of the thirteen united States of America" adopted by the "Representatives of the united States of America" on July 4, 1776.^[7] The current name was finalized on November 15, 1777, when the Second Continental Congress adopted the Articles of Confederation, the first of which states, "The Stile of this Confederacy shall be 'The United States of America.'" Common short forms and abbreviations of the United States of America include the United States, the U.S., the U.S.A., and America. Colloquial names for the country include the U.S. of A. and the States. Columbia, a once popular name for the Americas and the United States, was derived from Christopher Columbus. It appears in the name "District of Columbia". A female personification of Columbia appears on some official documents, including certain prints of U.S. currency.

The standard way to refer to a citizen of the United States is as an American. Though United States is the formal adjective, American and U.S. are the most common adjectives used to refer to the country ("American values," "U.S. forces"). American is rarely used in English to refer to people not connected to the United States.^[8]

The phrase "the United States" was originally treated as plural?e.g, "the United States are"?including in the Thirteenth Amendment to the Constitution, ratified in 1865. However, it became increasingly common to treat the name as singular?e.g., "the United States is"?after the end of the Civil War. The singular form is now standard, while the plural form is retained in the set idiom "these United States."^[9]

Geography

Topographic map of the contiguous United States

Climate zones of the contiguous United States

The coastal plain of the Atlantic seaboard gives way further inland to deciduous forests and the rolling hills of the Piedmont. The Appalachian Mountains divide the eastern seaboard from the Great Lakes and the grasslands of the Midwest. The Mississippi–Missouri River, the world's fourth longest river system, runs mainly north-south through the heart of the country. The flat, fertile prairie land of the Great Plains stretches to the west. The Rocky Mountains, at the western edge of the Great Plains, extend north to south across the continental United States, reaching altitudes higher than 14,000 feet (4,300 m) in Colorado.^[14] The area to the west of the Rocky Mountains is dominated by the rocky Great Basin and deserts such as the Mojave. The Sierra Nevada range runs parallel to the Rockies, relatively close to the Pacific coast. At 20,320 feet (6,194 m), Alaska's Mount McKinley is the country's tallest peak. Active volcanoes are common throughout the Alexander and Aleutian Islands, and the entire state of Hawaii is built upon tropical volcanic islands. The supervolcano underlying Yellowstone National Park in the Rockies is the continent's largest volcanic feature.^[15]

Because of the United States' large size and wide range of geographic features, nearly every type of climate is represented. The climate is temperate in most areas, tropical in Hawaii and southern Florida, polar in Alaska, semi-arid in the Great Plains west of the 100th meridian, desert in the Southwest, Mediterranean in Coastal California, and arid in the Great Basin. Extreme weather is not uncommon?the states bordering the Gulf of Mexico are prone to hurricanes, and most of the world's tornadoes occur within the continental United States, primarily in the Midwest's Tornado Alley.^[16]

Environment

The bald eagle has been the national bird of the United States since 1782

U.S. plant life is very diverse; the country has more than 17,000 identified native species of flora.^[17] More than 400 mammal, 700 bird, 500 reptile and amphibian, and 90,000 insect species have been documented.^[18] The Endangered Species Act of 1973 protects threatened and endangered species and their habitats, which are monitored by the U.S. Fish and Wildlife Service.

The U.S. has fifty-eight national parks and hundreds of other federally managed parks, forests, and wilderness areas.^[19] Altogether, the U.S. government regulates 28.8% of the country's total land area.^[20] Most such public land comprises protected parks and forestland, though some federal land is leased for oil and gas drilling,^[21] mining, or cattle ranching.

The energy policy of the United States is widely debated; many call on the country to take a leading role in fighting global warming.^[22] The United States is currently the second largest emitter, after the People's Republic of China, of carbon dioxide from the burning of fossil fuels.^[23]

History

Native Americans and European settlers

The indigenous peoples of the U.S. mainland, including Alaska Natives, are thought to have migrated from Asia. They began arriving at least 12,000 and as many as 40,000 years ago.^[24] Several indigenous communities in the pre-Columbian era developed advanced agriculture, grand architecture, and state-level societies. In 1492, Genoese explorer Christopher Columbus, under contract to the Spanish crown, reached several Caribbean islands, making first contact with the indigenous population. In the years that followed, the majority of the indigenous American peoples were killed by epidemics of Eurasian diseases.^[25]

The Mayflower transported Pilgrims to the New World in 1620, as depicted in William Halsall's The Mayflower in Plymouth Harbor, 1882

By 1674, English forces had won the former Dutch colonies in the Anglo-Dutch Wars; the province of New Netherland was renamed New York. Many new immigrants, especially to the South, were indentured servants?some two-thirds of all Virginia immigrants between 1630 and 1680.^[27] By the turn of the century, African slaves were becoming the primary source of bonded labor. With the 1729 division of the Carolinas and the 1732 colonization of Georgia, the thirteen British colonies that would become the United States of America were established. All had active local and colonial governments with elections open to most free men, with a growing devotion to the ancient rights of Englishmen and a sense of self government that stimulated support for republicanism. All had legalized the African slave trade. With high birth rates, low death rates, and steady immigration, the colonies doubled in population every twenty-five years. The Christian revivalist movement of the 1730s and 1740s known as the Great Awakening fueled interest in both religion and religious liberty. In the French and Indian War, British forces seized Canada from the French, but the francophone population remained politically isolated from the southern colonies. By 1770, those thirteen colonies had an increasingly Anglicized population of three million, approximately half that of Britain. Though subject to British taxation, they were given no representation in the Parliament of Great Britain.

Independence and expansion

Declaration of Independence, by John Trumbull, 1817?18

After the defeat of the British army by American forces who were assisted by the French, Great Britain recognized the sovereignty of the thirteen states in 1783. A constitutional convention was organized in 1787 by those who wished to establish a strong national government with power over the states. By June 1788, nine states had ratified the United States Constitution, sufficient to establish the new government; the republic's first Senate, House of Representatives, and president?George Washington?took office in 1789. New York City was the federal capital for a year, before the government relocated to Philadelphia. In 1791, the states ratified the Bill of Rights, ten amendments to the Constitution forbidding federal restriction of personal freedoms and guaranteeing a range of legal protections. Attitudes toward slavery were shifting; a clause in the Constitution protected the African slave trade only until 1808. The Northern states abolished slavery between 1780 and 1804, leaving the slave states of the South as defenders of the "peculiar institution." In 1800, the federal government moved to the newly founded Washington, D.C. The Second Great Awakening made evangelicalism a force behind various social reform movements.

Territorial acquisitions by date

Civil War and industrialization

Battle of Gettysburg, lithograph by Currier & Ives, ca. 1863

Immigrants landing at Ellis Island, New York, 1902

World War I, Great Depression, and World War II

An abandoned farm in South Dakota during the Dust Bowl, 1936

At the outbreak of World War I in 1914, the United States remained neutral. Americans sympathized with the British and French, although many citizens, mostly Irish and German, opposed intervention.^[33] In 1917, the United States joined the Allies, turning the tide against the Central Powers. Reluctant to be involved in European affairs, the Senate did not ratify the Treaty of Versailles, which established the League of Nations. The country pursued a policy of unilateralism, verging on isolationism.^[34] In 1920, the women's rights movement won passage of a constitutional amendment granting women's suffrage. Partly because of the service of many in the war, Native Americans gained U.S. citizenship in the Indian Citizenship Act of 1924.

During most of the 1920s, the United States enjoyed a period of unbalanced prosperity as farm profits fell while industrial profits grew. A rise in debt and an inflated stock market culminated in the 1929 crash that triggered the Great Depression. After his election as president in 1932, Franklin D. Roosevelt responded with the New Deal, a range of policies increasing government intervention in the economy. The Dust Bowl of the mid-1930s impoverished many farming communities and spurred a new wave of western migration. The nation would not fully recover from the economic depression until the industrial mobilization spurred by its entrance into World War II. The United States, effectively neutral during the war's early stages after the Nazi invasion of Poland in September 1939, began supplying materiel to the Allies in March 1941 through the Lend-Lease program.

On December 7, 1941, the United States joined the Allies against the Axis powers after a surprise attack on Pearl Harbor by Japan. World War II cost far more money than any other war in American history,^[35] but it boosted the economy by providing capital investment and jobs, while bringing many women into the labor market. Among the major combatants, the United States was the only nation to become richer?indeed, far richer?instead of poorer because of the war.^[36] Allied conferences at Bretton Woods and Yalta outlined a new system of international organizations that placed the United States and Soviet Union at the center of world affairs. As victory was achieved in Europe, a 1945 international conference held in San Francisco produced the United Nations Charter, which became active after the war.^[37] The United States, having developed the first nuclear weapons, used them on the Japanese cities of Hiroshima and Nagasaki in August. Japan surrendered on September 2, ending the war.^[38]

Cold War and civil rights

Martin Luther King, Jr. delivering his "I Have a Dream" speech, 1963

The United States and Soviet Union jockeyed for power after World War II during the Cold War, dominating the military affairs of Europe through NATO and the Warsaw Pact. The United States promoted liberal democracy and capitalism, while the Soviet Union promoted communism and a centrally planned economy. Both the United States and the Soviet Union supported dictatorships, and both engaged in proxy wars. United States troops fought Communist Chinese forces in the Korean War of 1950?53. The House Un-American Activities Committee pursued a series of investigations into suspected leftist subversion, while Senator Joseph McCarthy became the figurehead of anticommunist sentiment.

The Soviet Union launched the first manned spacecraft in 1961, prompting U.S. efforts to raise proficiency in mathematics and science and President John F. Kennedy's call for the country to be first to land "a man on the moon," achieved in 1969.^[39] Kennedy also faced a tense nuclear showdown with Soviet forces in Cuba. Meanwhile, America experienced sustained economic expansion. A growing civil rights movement headed by prominent African Americans, such as Martin Luther King, Jr., fought segregation and discrimination, leading to the abolition of Jim Crow laws. Following Kennedy's assassination in 1963, the Civil Rights Act of 1964 was passed under President Lyndon B. Johnson. Johnson and his successor, Richard Nixon, expanded a proxy war in Southeast Asia into the unsuccessful Vietnam War.

As a result of the Watergate scandal, in 1974 Nixon became the first U.S. president to resign, rather than be impeached on charges including obstruction of justice and abuse of power; he was succeeded by Vice President Gerald Ford. During the Jimmy Carter administration in the late 1970s, the U.S. economy experienced stagflation. The election of Ronald Reagan as president in 1980 marked a significant rightward shift in American politics, reflected in major changes in taxation and spending priorities.^[40] In the late 1980s and 1990s, the Soviet Union's power diminished, leading to its collapse.

Contemporary era

The leadership role taken by the United States and its allies in the United Nations?sanctioned Gulf War, under President George H. W. Bush, and later the Yugoslav wars helped to preserve its position as the world's last remaining superpower. The longest economic expansion in modern U.S. history?from March 1991 to March 2001?encompassed the administration of President Bill Clinton.^[41] In 1998, Clinton was impeached by the House on charges relating to a civil lawsuit and a sexual scandal, but he was acquitted by the Senate and remained in office.

The World Trade Center on the morning of September 11, 2001

The controversial presidential election of 2000 was resolved by a Supreme Court decision that effectively awarded the presidency to Texas governor George W. Bush, son of George H. W. Bush. On September 11, 2001, al-Qaeda terrorists struck the World Trade Center in New York City and The Pentagon near Washington, D.C., killing nearly three thousand people. In the aftermath, President Bush launched the War on Terrorism under a military philosophy stressing preemptive war now known as the Bush Doctrine. In late 2001, U.S. forces led a NATO invasion of Afghanistan, removing the Taliban government and al-Qaeda training camps. Taliban insurgents continue to fight a guerrilla war against the NATO-led force.

In 2002, the Bush administration began to press for regime change in Iraq on controversial grounds. Lacking the support of NATO or an explicit United Nations mandate for military intervention, Bush formed a Coalition of the Willing, and the U.S. invaded Iraq in 2003, removing President Saddam Hussein from power. Although facing both external^[42] and internal^[43] pressure to withdraw, the United States maintains its military presence in Iraq. The United States has been criticized for human rights violations in its pursuit of the War on Terrorism, including holding so-called enemy combatants at the Guantanamo Bay detention camp for years without trial and for its alleged use of torture.^[44] In the upcoming 2008 presidential election, the Republican Party candidate, Senator John McCain of Arizona, will face the Democratic Party candidate, Senator Barack Obama of Illinois, the first African American to head a major political party's presidential ticket.

Government and elections

The west front of the United States Capitol, which houses the United States Congress

The North Portico of the White House, home and work place of the U.S. president

The federal government is composed of three branches:

• Legislative: The bicameral Congress, made up of the Senate and the House of Representatives makes federal law, declares war, approves treaties, has the power of the purse, and has the power of impeachment, by which it can remove sitting members of the government.
• Executive: The president is the commander-in-chief of the military, can veto legislative bills before they become law, and appoints the Cabinet and other officers, who administer and enforce federal laws and policies.
• Judicial: The Supreme Court and lower federal courts, whose judges are appointed by the president with Senate approval, interpret laws and can overturn laws they deem unconstitutional.

The House of Representatives has 435 members, each representing a congressional district for a two-year term. House seats are apportioned among the fifty states by population every tenth year. As of the 2000 census, seven states have the minimum of one representative, while California, the most populous state, has fifty-three. Each state has two senators, elected at-large to six-year terms; one third of Senate seats are up for election every second year. The president serves a four-year term and may be elected to the office no more than twice. The president is not elected by direct vote, but by an indirect electoral college system in which the determining votes are apportioned by state. The Supreme Court, led by the Chief Justice of the United States, has nine members, who serve for life.

The front of the United States Supreme Court building

All laws and procedures of both state and federal governments are subject to review, and any law ruled in violation of the Constitution by the judicial branch is overturned. The original text of the Constitution establishes the structure and responsibilities of the federal government, the relationship between it and the individual states, and essential matters of military and economic authority. Article One protects the right to the "great writ" of habeas corpus, and Article Three guarantees the right to a jury trial in all criminal cases. Amendments to the Constitution require the approval of three-fourths of the states. The Constitution has been amended twenty-seven times; the first ten amendments, which make up the Bill of Rights, and the Fourteenth Amendment form the central basis of individual rights in the United States.

Parties and politics

Politics in the United States have operated under a two-party system for virtually all of the country's history. For elective offices at all levels, state-administered primary elections are held to choose the major party nominees for subsequent general elections. Since the general election of 1856, the two dominant parties have been the Democratic Party, founded in 1824 (though its roots trace back to 1792), and the Republican Party, founded in 1854. Since the Civil War, only one third-party presidential candidate?former president Theodore Roosevelt, running as a Progressive in 1912?has won as much as 20% of the popular vote.

The incumbent president, Republican George W. Bush, is the 43rd president in the country's history. All U.S. presidents to date have been white men. If Democrat Barack Obama wins the forthcoming presidential election, he will become the first African-American president. Following the 2006 midterm elections, the Democratic Party controls both the House and the Senate. Every member of the U.S. Congress is a Democrat or a Republican except two independent members of the Senate?one a former Democratic incumbent, the other a self-described socialist. An overwhelming majority of state and local officials are also either Democrats or Republicans.

Within American political culture, the Republican Party is considered "center-right" or conservative and the Democratic Party is considered "center-left" or liberal, but members of both parties have a wide range of views. In a May 2008 poll, 44% of Americans described themselves as "conservative," 27% as "moderate," and 21% as "liberal."^[47] On the other hand, that same month a plurality of adults, 41.7%, identified as Democrats, 31.6% as Republicans, and 26.6% as independents.^[48] The states of the Northeast and West Coast and some of the Great Lakes states are relatively liberal-leaning—they are known in political parlance as "blue states." The "red states" of the South and the Rocky Mountains lean conservative.

States

The United States is a federal union of fifty states. The original thirteen states were the successors of the thirteen colonies that rebelled against British rule. Most of the rest have been carved from territory obtained through war or purchase by the U.S. government. The exceptions are Vermont, Texas, and Hawaii; each was an independent republic before joining the union. Early in the country's history, three states were created out of the territory of existing ones: Kentucky from Virginia; Tennessee from North Carolina; and Maine from Massachusetts. West Virginia broke away from Virginia during the American Civil War. The most recent state?Hawaii?achieved statehood on August 21, 1959. The U.S. Supreme Court has ruled that the states do not have the right to secede from the union.

The states compose the vast bulk of the U.S. land mass; the only other areas considered integral parts of the country are the District of Columbia, the federal district where the capital, Washington, is located; and Palmyra Atoll, an uninhabited but incorporated territory in the Pacific Ocean. The United States possesses five major territories with indigenous populations: Puerto Rico and the United States Virgin Islands in the Caribbean; and American Samoa, Guam, and the Northern Mariana Islands in the Pacific. Those born in the territories (except for American Samoa) possess U.S. citizenship.

Foreign relations and military

President George W. Bush (right) with UK prime minister Gordon Brown

The United States has vast economic, political, and military influence on a global scale, which makes its foreign policy a subject of great interest around the world. Almost all countries have embassies in Washington, D.C., and many host consulates around the country. Likewise, nearly all nations host American diplomatic missions. However, Cuba, Iran, North Korea, Bhutan, Sudan, and the Republic of China (Taiwan) do not have formal diplomatic relations with the United States.

American isolationists have often been at odds with internationalists, as anti-imperialists have been with promoters of Manifest Destiny and American Empire. American imperialism in the Philippines drew sharp rebukes from Mark Twain, philosopher William James, and many others. Later, President Woodrow Wilson played a key role in creating the League of Nations, but the Senate prohibited American membership in it. Isolationism became a thing of the past when the United States took a lead role in founding the United Nations, becoming a permanent member of the Security Council and host to the United Nations Headquarters. The United States enjoys a special relationship with the United Kingdom and strong ties with Australia, New Zealand, Japan, Israel, and fellow NATO members. It also works closely with its neighbors through the Organization of American States and free trade agreements such as the trilateral North American Free Trade Agreement with Canada and Mexico. In 2005, the United States spent $27.3 billion on official development assistance, the most in the world; however, as a share of gross national income (GNI), the U.S. contribution of 0.22% ranked twentieth of twenty-two donor states. On the other hand, nongovernmental sources such as private foundations, corporations, and educational and religious institutions donated $95.5 billion. The total of $122.8 billion is again the most in the world and seventh in terms of GNI percentage.^[49]

The USS Ronald Reagan aircraft carrier

The president holds the title of commander-in-chief of the nation's armed forces and appoints its leaders, the secretary of defense and the Joint Chiefs of Staff. The United States Department of Defense administers the armed forces, including the Army, the Navy, the Marine Corps, and the Air Force. The Coast Guard falls under the jurisdiction of the Department of Homeland Security in peacetime and the Department of the Navy in times of war. In 2005, the military had 1.38 million personnel on active duty,^[50] along with several hundred thousand each in the Reserves and the National Guard for a total of 2.3 million troops. The Department of Defense also employs approximately 700,000 civilians, disregarding contractors. Military service is voluntary, though conscription may occur in wartime through the Selective Service System. The rapid deployment of American forces is facilitated by the Air Force's large fleet of transportation aircraft and aerial refueling tankers, the Navy's fleet of eleven active aircraft carriers, and Marine Expeditionary Units at sea in the Navy's Atlantic and Pacific fleets. Outside of the American homeland, the U.S. military is deployed to 770 bases and facilities, on every continent except Antarctica.^[51] Because of the extent of its global military presence, scholars describe the United States as maintaining an "empire of bases."^[52]

Total U.S. military spending in 2006, over $528 billion, was 46% of the entire military spending in the world and greater than the next fourteen largest national military expenditures combined. (In purchasing power parity terms, it was larger than the next six such expenditures combined.) The per capita spending of $1,756 was approximately ten times the world average.^[53] At 4.06% of GDP, U.S. military spending is ranked 27th out of 172 nations.^[54] The proposed base Department of Defense budget for 2009, $515.4 billion, is a 7% increase over 2008 and a nearly 74% increase over 2001.^[55] The estimated total cost of the Iraq War to the United States through 2016 is $2.267 trillion.^[56] As of June 6, 2008, the United States had suffered 4,092 military fatalities during the war and nearly 30,000 wounded.^[57]

Economy

The United States has a capitalist mixed economy, which is fueled by abundant natural resources, a well-developed infrastructure, and high productivity. According to the International Monetary Fund, the United States GDP of more than $13 trillion constitutes over 25.5% of the gross world product at market exchange rates and over 19% of the gross world product at purchasing power parity (PPP).^[2] The largest national GDP in the world, it was slightly less than the combined GDP of the European Union at PPP in 2006.^[64] The country ranks eighth in the world in nominal GDP per capita and fourth in GDP per capita at PPP.^[2] The United States is the largest importer of goods and third largest exporter, though exports per capita are relatively low. Canada, China, Mexico, Japan, and Germany are its top trading partners.^[65] The leading export commodity is electrical machinery, while vehicles constitute the leading import.^[66]

The private sector constitutes the bulk of the economy, with government activity accounting for 12.4% of GDP. The economy is postindustrial, with the service sector contributing 67.8% of GDP.^[67] The leading business field by gross business receipts is wholesale and retail trade; by net income it is finance and insurance.^[68] The United States remains an industrial power, with chemical products the leading manufacturing field.^[69] The United States is the third largest producer of oil in the world.^[70] It is the world's number one producer of electrical and nuclear energy, as well as liquid natural gas, sulfur, phosphates, and salt. While agriculture accounts for just under 1% of GDP,^[67] the United States is the world's top producer of corn^[71] and soybeans.^[72] The country's leading cash crop is marijuana, despite federal laws making its cultivation and sale illegal.^[73] The New York Stock Exchange is the world's largest by dollar volume.^[74] Coca-Cola and McDonald's are the two most recognized brands in the world.^[75]

Wall Street is home to the New York Stock Exchange (NYSE)

In 2005, 155 million persons were employed with earnings, of whom 80% worked in full-time jobs.^[76] The majority, 79%, were employed in the service sector.^[10] With approximately 15.5 million people, health care and social assistance is the leading field of employment.^[77] About 12% of American workers are unionized, compared to 30% in Western Europe.^[78] The U.S. ranks number one in the ease of hiring and firing workers, according to the World Bank.^[79] Between 1973 and 2003, a year's work for the average American grew by 199 hours.^[80] Partly as a result, the United States maintains the highest labor productivity in the world. However, it no longer leads the world in productivity per hour as it did from the 1950s through the early 1990s; workers in Norway, France, Belgium, and Luxembourg are now more productive per hour.^[81] The United States ranks third in the World Bank's Ease of Doing Business Index.^[79] Compared to Europe, U.S. property and corporate income taxes are generally higher, while labor and, particularly, consumption taxes are lower.^[82]

Income and human development

Inflation adjusted percentage increase in after-tax household income for the top 1% and four quintiles, between 1979 and 2005 (gains by top 1% are reflected by bottom bar; bottom quintile by top bar)^[83]

Between 1967 and 2006, median household income rose 30.8% in constant dollars, largely because of the growing number of dual-earner households.^[62] Though the standard of living has improved for nearly all classes since the late 1970s,^[89] income inequality has grown substantially.^[90] The share of income received by the top 1% has risen considerably while the share of income of the bottom 90% has fallen, with the gap between the two groups being roughly as large in 2005 as in 1928.^[91] According to the standard Gini index, income inequality in the United States is higher than in any European nation.^[92] Some economists, such as Alan Greenspan, see rising income inequality as a cause for concern.^[93] Wealth is highly concentrated: The richest 10% of the adult population possesses 69.8% of the country's household wealth, the second-highest share of any democratic developed nation.^[94] The top 1% possesses 33.4% of net wealth.^[95]

Science and technology

Astronaut Buzz Aldrin during the first human landing on the Moon, 1969

The United States has been a leader in scientific research and technological innovation since the late nineteenth century. In 1876, Alexander Graham Bell was awarded the first U.S. patent for the telephone. The laboratory of Thomas Edison developed the phonograph, the first long-lasting light bulb, and the first viable movie camera. In the early twentieth century, the automobile companies of Ransom E. Olds and Henry Ford pioneered assembly line manufacturing. The Wright brothers, in 1903, made what is recognized as the "first sustained and controlled heavier-than-air powered flight."^[96] The rise of Nazism in the 1930s led many important European scientists, including Albert Einstein and Enrico Fermi, to immigrate to the United States. During World War II, the U.S.-based Manhattan Project developed nuclear weapons, ushering in the Atomic Age. The Space Race produced rapid advances in rocketry, materials science, and computers. The United States largely developed the ARPANET and its successor, the Internet. Today, the bulk of research and development funding, 64%, comes from the private sector.^[97] The United States leads the world in scientific research papers and impact factor.^[98] Americans enjoy high levels of access to technological consumer goods.^[99] Almost half of U.S. households have broadband Internet service.^[100] The country is the primary developer and grower of genetically modified food; more than half of the world's land planted with biotech crops is in the United States.^[101]

Transportation

Interstate 80, the second-longest U.S. Interstate highway, runs from California to New Jersey

Energy

The United States energy market is 29,000 terawatt hours per year. Energy consumption per capita is 7.8 tons of oil equivalent per year, compared to Germany's 4.2 tons and Canada's 8.3 tons. In 2005, 40% of the nation's energy came from petroleum, 23% from coal, and 22% from natural gas. The remainder was supplied by nuclear power and various renewable energy sources.^[110] The United States is the world's largest consumer of petroleum.^[111] For decades, nuclear power has played a limited role relative to many other developed countries. Recently, applications for new nuclear plants have been filed.^[112]

Demographics

Largest ancestry groups by county, 2000

The United States has a very diverse population?thirty-one ancestry groups have more than a million members.^[120] Whites are the largest racial group, with German Americans, Irish Americans, and English Americans constituting three of the country's four largest ancestry groups.^[120] African Americans constitute the nation's largest racial minority and third largest ancestry group.^[121][120] Asian Americans are the country's second largest racial minority; the two largest Asian American ancestry groups ar