The United States is home to vastly more immigrants than any other country in the world, but its immigrant population is less diverse than many other nations, with more than a fourth of foreign-born residents originating from a single country: Mexico.

In a new compilation of immigration facts, the Pew Research Center examines U.S. migration patterns compared to the rest of the globe — highlighting that, with 46.6 million immigrants as of 2015, the U.S. “by a wide margin” has the most foreign-born people living within its borders.

“As of 2015, the United Nations estimates that 46.6 million people living in the United States were not born there. This means that about one-in-five international migrants (19%) live in the U.S.,” the report reads. “The U.S. immigrant population is nearly four times that of the world’s next largest immigrant destination – Germany, with about 12 million immigrants.”

The U.S.-Mexico border is also the world’s largest migration corridor, as Pew details. With some 12 million Mexico-born immigrants living in the U.S., the migration route dwarfs the second largest corridor between India and the United Arab Emirates — where 3.5 million Indian immigrants reside.

While the U.S. has the largest population of newcomers and immigrants from almost every country within its borders, the total immigrant population is not as diverse as other countries.

“Roughly one-in-four (26%) immigrants in the U.S. come from just one country, Mexico. In several other destination countries (mainly in Europe), immigrants are not as concentrated from a single country or handful of them,” Pew reports.

Perhaps counterintuitively, although the proportion of foreign-born people in the U.S. is at a record high (one-in-seven U.S. residents are immigrants), other countries have a greater share of immigrants that the U.S.

“By way of comparison, about one-in-five people in Canada (22%) are foreign born,” Pew reports. “In Australia, it’s nearly three-in-ten people (28%). And in some Persian Gulf countries such as Qatar (75%) and United Arab Emirates (88%), the great majority of their resident populations are immigrants, many who have been actively recruited as foreign labor.”

Finally, although the U.S. sees a lot of incoming traffic, the outgoing flow is relatively low.

According to Pew a little over 3 million Americans live in other countries compared to 16 million Indian emigrants and 12 million Mexicans — who are largely living the U.S.

“Even less-populated countries like Syria (5 million) and Poland (4.4 million) have larger emigrant populations,” Pew reports. “As a share of the population in 2015, around 1% of Americans born in the United States lived outside of the United States. This is a considerably smaller share than that of other migrant destinations like the UK (8%), Germany (5%) or Canada (4%).”