In March 2019, KBS2’s weekend drama My Only One ended with a household rating of 49.4%. JTBC’s SKY Castle, the show that spawned parodies online and off that winter, peaked a little under 24%. On paper, the family drama rated about twice as high.
Then look only at viewers aged 20 to 49. My Only One peaked at 16.24% there, and SKY Castle at 14.8%. The gap mostly disappears. Both figures are real and both come from the same kind of measurement. They’re just counting different people, and the first one is the number you usually see quoted.
What the percentage is a percentage of
Korean press calls it sicheongryul (시청률, “viewing rate”), and the default version is the gagu (가구, “household”) rating. Ratings companies pick panel homes by monthly income, age, region, and household size, then put a meter on the TV. If 100 of every 1,000 TV homes have the channel on, that’s 10%. It doesn’t matter whether one person was watching or five. When a Korean entertainment article gives a rating, it usually credits Nielsen Korea.
The panel is small. A 2021 Media Today report from an academic conference put it at about 4,000 households, and the speakers there went through what that misses. Phones, PCs, and VOD aren’t in it. A Yonsei adjunct professor noted that news channels, which people often watch on screens in subway stations and restaurants, don’t get credit for those viewers, since those TVs aren’t surveyed.
My favorite detail from that report is the 0% rating. Some programs with real viewers still come back at zero because the panel is too small to catch them, and broadcasters complain often, since they sell ads off the number. A researcher from Nielsen’s Korean side agreed it was a limit: avoiding zeros would take more panel homes, and more homes are harder to manage.
Why 3% on cable used to be daebak
In 2015, Kyunghyang Shinmun ran a headline asking why a cable show that tops 3% gets called daebak (대박, “jackpot”). On terrestrial channels, a drama under 10% was described as struggling, and 4 to 5% brought talk of cancellation. Cable had settled on 3% as its bar. The cast of tvN’s Misaeng had promised fans chicken and beer if the show reached 3%. Its last episode did 8.2%.
I get why people assume cable just reaches fewer homes, so its percentages run small. The article says otherwise. It called the popular line that “10% on cable equals 30% on terrestrial” baseless, because the survey samples don’t differ much. Cable channels gave two other reasons: the people watching TV at home skewed toward their 40s and 50s and preferred the terrestrial channels they knew, and the count only saw the TV set.
The bar kept moving after that. SKY Castle’s finale in February 2019 made it the highest-rated series in Korean cable history at the time.
The number networks actually judge themselves by
The age-band rating in the intro is the 2049 rating, the individual rating among viewers aged 20 to 49. Yonhap describes it as the core measure most Korean broadcasters have used for channel and program performance, because that age group was considered the strongest buyer for TV advertising. Economy Chosun read My Only One’s near-50% as driven by viewers over 50, and quoted a studio official saying an all-ages household rating isn’t a figure that persuades advertisers.
On January 1, 2026, MBC moved its own line from 2049 to 2054. It cited an aging population and how much TV people aged 50 to 54 watch. By MBC’s analysis, I Live Alone’s 2049 rating for January to November 2025 was 3.3%, and 3.8% counted the new way.
I think that’s a reasonable change, and I find it a little funny that the fix for a metric leaving out older viewers was to let five more years of them in. The first drama MBC announced in 2054 terms was The Judge Returns, and its first episode came in at 1.6% on that measure.