I guess, you also need to see the other ratings data, which is the demographic ratings. This rating is important, as it could tell which network could make or break with advertisers, that help them make money for their content.
Last month, SBS was the most watched network in primetime demos, while KBS2 was the most watched the whole day. However, JTBC is the most watched cable network on both primetime and whole day demos, beating MBC in the process. It’s the first time that a cable network had beaten a commercial free to air network in demos. Also, tvN had also double the demos of KBS1 (KBS mngt. doesn’t care since KBS1 is a license-fee supported channel. But if a channel skews more older viewers, is it worth their license fee?)
So, what does this mean? Although MBC got higher overall ratings, majority of their viewers are outside the important demos. Lower demo ratings mean lower ad revenue.
At the same time, advertisers will flock in to either JTBC or tvN, because they have younger viewers. No wonder why tvN was able to add a Wednesday-Thursday drama line up, because although the rate low overall, advertisers love them because they have the viewers that they want.
Also, I don’t see JTBC adding a drama line up in the future, since their primetime schedule is filled with variety shows. And they rate very well, that it sometimes beat the terrestrial networks’ programs in demo and overall ratings. So, why change when nothing’s broken, right?