Forbes Celebrity 40 is determined by first taking the top 100 most searched people of the year (data provided by Nate) and ranking them based on 4 different measures:
1. Sales - estimated based on appearance fees, CF guarantees album sales, etc. + reported overseas income
2. Media exposure - number of apperances in the top 3 newspapers, covers of 8 magazines, Ilgan Sports
3. Television exposure - CF model ranking and appearances on talk shows and variety shows
4. Professionalism - TV ratings for actors/MCs, total audience for movie actors, Gaon digital and physical sales rankings for singers, competition results for athletes
Final list is the 40 celebrities with the highest average ranking across all 4 categories.
*Note that sales especially are subject to error because data may not always be complete.
Korean source: link
Translation source: link
(note: It also appears IU ranked 8th overall for sales)
