In recent years, about one-fifth of the students attending summer classes at UC Berkeley have hailed from countries beyond the campus’s own.

The campus’ summer classes have been open to international visitors since they began in 1899, according to Rick Russo, the dean for summer sessions, study abroad and lifelong learning. About 4,000 of the approximately 16,000 students are visiting, and of that group, about 3,000 are international.

With its summer session program, the campus brought in revenue of about $7.6 million in 2013, $9 million last year and $8.8 million this year, according to campus spokesperson Dan Mogulof.

The campus charges visiting international students $460 per unit for summer classes — about $50 more than the $406 per unit charged to UC undergraduate students. The campus also charges a $300 international service fee for some, although visiting students do not pay the $212 one-time campus fee charged to UC students.

Although a language difference may serve as a barrier in some classes, the campus also offers classes in its College Writing Programs that cater to non-native English speakers. In doing so, it allows international visitors to “have a Berkeley experience, regardless of … their English language proficiency,” Russo said in an email statement.

See the above map for a comprehensive look at where this summer’s visiting international students call home. About half —1,676 students — come from China, while 170, 291, 120 and 171 come from Hong Kong, South Korea, Singapore and Taiwan, respectively. Other countries are represented in the summer session’s visiting population in smaller numbers, ranging from one student — as in the case of Nigeria, Romania and Colombia — to dozens.