Religion is the main driver

In 2008, countries in the Middle East and some parts of Africa and Southwest Asia had circumcision rates as high as 80 percent, while in other parts of Asia, and in Europe and South America, the number was closer to 20 percent, according to World Health Organization data about the influence of religion on circumcision.

South Korea is one of the few countries where a high circumcision rate isn't prompted by religious doctrine, and it's the only one among its near neighbors where the practice is routine, even though it was virtually unknown on the Korean Peninsula until Japanese rule ceased at the end of World War II.

In 1945, 0.1 percent of the peninsula's male population was circumcised, but since then the rate among boys of high-school age in South Korea has risen to 90 percent. Some scholars attribute the increase to the long-term presence of a large contingent of US military in the years following WWII.