Prosperity.

As a result of growing agricultural yields and increased manufacturing production, the people of the United States in the 1910s were in aggregate the richest in the world. By 1913 the United States was producing nearly a third of the worldwide manufacturing output, and its $37 billion national income in 1914 was more than triple that of its nearest competitors, Great Britain and Germany. The per-capita income of the nearly one hundred million U.S. inhabitants in 1914 was $377, more than one and a half times that of Great Britain, twice that of Germany, and almost ten times that of Russia. As the historian Paul Kennedy has noted, "The United States seemed to have all the economic advantages which some of the other powers possessed in part, but none of their disadvantages." America's aggregate wealth was enormous, but the distribution of these riches was highly skewed...