First, the part that lets people in. The United States grants legal permanent resident status — better known as a green card — to about one million people each year. The actual numbers, according to the Department of Homeland Security 2012 Yearbook of Immigration Statistics — the most recent full set of data available — were 1,031,631 in 2012; 1,062,040 in 2011; 1,042,625 in 2010; and so on going back. Legal permanent resident status is what it sounds: a recipient can stay in the United States permanently, and become a citizen if he or she chooses.

“We are the most generous nation on earth to immigrants, allowing over one million people a year to come here legally,” wrote Sen. Rubio in 2013. The new million each year come from all around the world, with heavy concentrations in a few places. According to the Yearbook, in 2012, 416,488 came from Asia, while 389,526 came from Mexico, the Caribbean and Central America. That’s a lot of the million right there; other sources include 103,685 from Africa and 86,956 from Europe.

Of the total, the vast majority — 680,799 in 2012 — were given green cards because they have family members in the United States. A much smaller group, 143,998, were admitted for employment reasons. The rest were given refugee status, or asylum, or came from the so-called “diversity” lottery.