That is why it is so important for a course rating to accurately reflect the difficulty of the course. For older courses, re-rating is often necessary because of course reconstruction. A course may have redesigned a hole, added or lost trees, bunkers or water or changed the course boundaries. All of these factors affect the overall rating. Even if no reconstruction has taken place, nature can affect the rating as well.
Trees grow, greens harden and bunkers settle.
As a course matures, it generally takes on a tougher rating. Nearly all courses within the United States have been measured and rated using the U.S. Golf Association's rating and slope guidelines. This allows golfers to report their scores from any course in the country for handicapping purposes. Without a universal course and slope rating system, this would be impossible. The MGA coordinates its rating team's efforts through the MGA office.