Notes

14. English is the official language of 32 states; English and Hawaiian are both official languages in Hawaii, and English and 20 Indigenous languages are official in Alaska. Algonquian, Cherokee, and Sioux are among many other official languages in Native-controlled lands throughout the country. French is a de facto, but unofficial, language in Maine and Louisiana, while New Mexico law grants Spanish a special status.^[4][5][6][7]
15. 
    
16. In five territories, English as well as one or more indigenous languages are official: Spanish in Puerto Rico, Samoan in American Samoa, Chamorro in both Guam and the Northern Mariana Islands. Carolinian is also an official language in the Northern Mariana Islands.
17. 
    
18. Whether the United States or China is larger has been disputed. The figure given is from the U.S. Census and United Nations.^[12]
19. 
    
20. See Time in the United States for details about laws governing time zones in the United States.
21. 
    
22. Except American Samoa and the Virgin Islands.
23. 
    
24. The five major territories are American Samoa, Guam, the Northern Mariana Islands, Puerto Rico, and the United States Virgin Islands. There are eleven smaller island areas without permanent populations: Baker Island, Howland Island, Jarvis Island, Johnston Atoll, Kingman Reef, Midway Atoll, and Palmyra Atoll. U.S. sovereignty over Bajo Nuevo Bank, Navassa Island, Serranilla Bank, and Wake Island is disputed.^[20]
25. 
    
26. The following two primary sources (non-mirrored) represent the range (min./max.) of total area for China and the United States. Both sources exclude Taiwan from the area of China.
    1. The Encyclopædia Britannica lists China as world's third-largest country (after Russia and Canada) with a total area of 9,572,900 sq km,^[22] and the United States as fourth-largest at 9,526,468 sq km. The figure for the United States is less than in the CIA Factbook because it excludes coastal and territorial waters.^[23]
    2. The CIA World Factbook lists the United States as the third-largest country (after Russia and Canada) with total area of 9,833,517 sq km,^[24] and China as fourth-largest at 9,596,960 sq km.^[25] This figure for the United States is greater than in the Encyclopædia Britannica because it includes coastal and territorial waters.
27. 
    
28. The United States has a very diverse population; 37 ancestry groups have more than one million members.^[226] German Americans are the largest ethnic group (more than 50 million) – followed by Irish Americans (circa 37 million), Mexican Americans (circa 31 million) and English Americans (circa 28 million).^[227][228] White Americans are the largest racial group; black Americans are the nation's largest racial minority (note that in the U.S. Census, Hispanic and Latino Americans are counted as an ethnic group, not a "racial" group), and third-largest ancestry group.^[226] Asian Americans are the country's second-largest racial minority; the three largest Asian American ethnic groups are Chinese Americans, Filipino Americans, and Indian Americans.^[226]
29. 
    
30. Fertility is also a factor; in 2010 the average Hispanic woman gave birth to 2.35 children in her lifetime, compared to 1.97 for non-Hispanic black women and 1.79 for non-Hispanic white women (both below the replacement rate of 2.1).^[242] Minorities (as defined by the Census Bureau as all those beside non-Hispanic, non-multiracial whites) constituted 36.3% of the population in 2010 (this is nearly 40% in 2015),^[243] and over 50% of children under age one,^[244] and are projected to constitute the majority by 2042.^[245] This contradicts the report by the National Vital Statistics Reports, based on the U.S. census data, which concludes that 54% (2,162,406 out of 3,999,386 in 2010) of births were non-Hispanic white.^[242] The Hispanic birth rate plummeted 25% between 2006 and 2013 while the rate for non-Hispanics decreased just 5%.^[246]
31. 
    
32. Source: 2010 American Community Survey, U.S. Census Bureau. Most respondents who speak a language other than English at home also report speaking English "well" or "very well." For the language groups listed above, the strongest English-language proficiency is among speakers of German (96% report that they speak English "well" or "very well"), followed by speakers of French (93.5%), Tagalog (92.8%), Spanish (74.1%), Korean (71.5%), Chinese (70.4%), and Vietnamese (66.9%).
33. 
    
34. In January 2015, U.S. federal government debt held by the public was approximately $13 trillion, or about 72% of U.S. GDP. Intra-governmental holdings stood at $5 trillion, giving a combined total debt of $18.080 trillion.^[366][367] By 2012, total federal debt had surpassed 100% of U.S. GDP.^[368] The U.S. has a credit rating of AA+ from Standard & Poor's, AAA from Fitch, and AAA from Moody's.^[369]
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36. The Stockholm International Peace Research Institute, SIPRI, found that the United States' arms industry was the world's biggest exporter of major weapons from 2005 to 2009,^[431] and remained the largest exporter of major weapons during a period between 2010 and 2014, followed by Russia, China (PRC), and Germany.^[432]
37. 
    
Droughts are likely to particularly affect the 66 percent of Americans whose communities depend on surface water.^[510] As for drinking water quality, there are concerns about disinfection by-products, lead, perchlorates and pharmaceutical substances, but generally drinking water quality in the U.S. is good.^[511]