Complex sentence: The Office of Inspector General (OIG) of the United States Postal Service was created by federal statute in 1996, assuming the duties previously carried out by the United State Postal Inspection Service performed the duties of the OIG.
Split into simpler sentences: The Office of Inspector General (OIG) of the U.S. Postal Service was authorized by law in 1996. Prior to the 1996 legislation, the U.S. Postal Inspection Service performed the duties of the OIG.