From 1860 to 1910, between 13 percent and 15 percent of people in the United States were born in another country. After 1910, the share of the population composed of the foreign born began a steady decline, falling to less than 5 percent by 1970. But that share has increased rapidly since 1970, reaching about 13 percent in the past few years. About 40 million foreign-born people now live in the United States. Of that group, not quite half have fulfilled the requirements of U.S. citizenship. Of the remaining people, about half are authorized to live and work in the United States, and about half are not authorized to live or work in the country.