Some interesting data have become public about the percentage of U.S. military personnel who commit offenses in South Korea and are prosecuted by host state authorities. According to this Yonhap article:
Fewer than half of the U.S. soldiers stationed in South Korea who allegedly committed crimes in the past five years were indicted by South Korea, a government report showed Thursday.
In the report to the National Assembly's Legislation and Judiciary Committee, the Ministry of Justice said a total of 1,766 U.S. servicemen were implicated in crimes between 2010 and June 2015, but only 503 were indicted by South Korean prosecutors.
South Korean law enforcement authorities turned over 893 U.S. soldiers suspected of committing crimes to the U.S. Forces Korea (USFK) in the same period, in accordance with a clause in the South Korea-U.S. Status of Forces Agreement, the report said.
The relevant clause stipulates that South Korean authorities have priority in exercising jurisdiction over U.S. soldiers implicated in crimes, except for when crimes are committed by a soldier on duty.
Overturning a lower court ruling, the Seoul High Court on Monday ruled the government does not have to disclose the criminal records of U.S. soldiers when jurisdiction has been given up by South Korea under the SOFA.