Freeman points out that for the United States immigration per year – as a share of U.S. population – actually shrank from 1910 to 1970. But today, there are 35 million immigrants in the United States; this is 12 percent of the population, more than double the 4.7 percent in 1970. The recent rise in the level of debate over immigration reflects this proportional increase in the U.S. immigrant population.