The ranking score is used to determine how "popular" a trip or location is. It is calculated based off of a weighted average of the number of reviews and the user ratings. For example, a trip with 2 reviews and an average rating of 5 will have a lower "ranking score" than one with 10 reviews and an average rating of 4. This is because even though the first trip has a better average rating, it has not been reviewed as much as the second trip, so it is not as "popular". In the future we may modify the ranking score to take in additional factors, such as the number of views, comments, and photos.