How are courses rated?
OGA is responsible for rating courses in Oregon and SW Washington. Each course is rated once every 7-8 years, more often if there are enough changes to the course to deem it necesary. Very basically, landing zones are analyzed for Scratch and Bogey, Male and Female golfers, from each set of tees. Difficulty is assessed for each Obstacle: topography, fairway, recoverability and rough, bunkers, water, trees, green target and surface. Also considered are factors such as roll, wind and altitude. The primary factor of Course Rating is having an accurate yardage of the course.
If you would like to learn more, here is a link to a series of articles about Course Rating: http://oga.org/handicaps/tee-green-and-all-between-course-rating-primer