The Congressional Budget Office takes stock (pdf) of the US immigrant population:
From 1860 to 1910, between 13 percent and 15 percent of people in the United States were born somewhere else. After 1910, that share of the population began a steady decline, falling to less than 5 percent by 1970, when the trend reversed. Between 1970 and 2000, the foreign- born population increased from 9.6 million to 31.5 million. In the 1970s, the rate of increase was about 0.4 million people per year; in the 1980s, the rate was about 0.6 million people per year; and in the 1990s, the rate was about 1.1 million people per year. The rate of increase slowed slightly during the 2000s, when about 0.8 million foreign-born people were added to the U.S. population each year. By 2009, 38.5 million people were for- eign born. That group constituted roughly 12.5 percent of the U.S. population, about the same percentage as in the early part of the 20th century.
The Dish 