Frank Kogan

From Wikip:

Physical album sales from LOEN Entertainment, SM Entertainment, Sony Music Korea, Warner Music Korea, Universal Music, and Mnet Media are synthesized in the album chart. All music sales except physical sales is estimated by digital chart. The digital chart is the combination of the mobile chart and the online chart. The mobile chart estimates the best selling ringtones, while the online chart calculates downloads and bgm sales as well as streaming services. All charts are offered monthly and weekly. [emphasis added]

It's that first sentence that jumped out at me as making the chart particularly untrustworthy. I can't tell if the companies are doing the sales reporting themselves; but otherwise, why list them like that? Not that physical sales are dominant anymore, or albums, but how can you be trustworthy if you're getting your figures from the labels, not the retailers. Or course, retailers can accept payola and lie too, which is why Billboard started using Soundscan in the U.S. And any system can be gamed, and it's the big guys who are likely to win the gaming. My guess is that in several years Gaon will be closer to genuinely reliable. Of course illegal downloads totally skew the picture anyway, and that's not going to change; though maybe there's a reasonable way to estimate which genres get illegally downloaded more than others, and which sales patterns have stronger correlations to illegal downloads than others do. But it'll never really be scientifically possible to gauge a song's popularity with complete numerical accuracy.