Korean Drama Ratings Explained: Hotel del Luna got 10%, which means?

Yeo Jin-goo and IU’s Hotel del Luna recently obtained a nationwide TV rating of 10.4 percent. Ok, 10% for a series airing on cable TV? That’s great! Most of us K-drama fans know that the series is doing very well based on that number, but some are still confused about how big 10% is for a cable show, or what does that figure is really supposed to mean. I want to erase that confusion with this article and give a benchmark for the average ratings of Korean dramas.

Korean drama TV ratings defined

In South Korea, a TV rating is an estimate of the percentage of households watching a particular program. Again, it is just an estimate, which is calculated using a sample that represents the 20-21 million homes in Korea that own TVs. In 2011, that representative sample (for Nielsen Korea) was made up of 2,050 households (my efforts to find the current sample size were to no avail). Maybe the number is much larger now but assuming it did not increase at all in the last eight years, the ratings we know today are derived from just 0.01 percent of the total no. of TV equipped households in Korea (there are now 22 million households in the country, 95-98% or around 21 million of which have TVs). Obviously, Nielsen’s sample is just tiny.

If a drama gets a nationwide rating of, let’s say, 8%, what it really means is an estimated 8 percent of the total households in the representative sample had watched the drama. But since this sample represents the entire population, we could say that close to 8% of the total no. of TV equipped households in Korea had tuned in to watch the program. On the flip side, 92% of the households watched other shows or didn’t watch TV at all. You must also know that this 8% is the average for a specified period (usually from 10 to 11 p.m. for terrestrial Korean dramas) since ratings change every second or minute when people switch channels in the middle of an episode. We’re talking about households here, NOT individual viewers—two people might be watching in one home, six in another.

Hotel del Luna Poster

However, Nielsen can also count the number of individual viewers who watched a drama because it extrapolates from the sample and estimates the number of viewers in the entire population watching the series. Now, let’s use Hotel del Luna as an example to understand what I have just explained. The drama’s August 18 episode recorded a nationwide rating of 10.407 percent, which means that an estimated 10.4 percent of the cable TV equipped households in Korea watched that episode. OK, but we have really no idea as to how many people actually watched it since most K-drama news websites (e.g. Dramabeans, Soompi, and even Kdramapal) report only the ratings. When you go to Nielsen Korea’s website, however, you can see this information—the August 18 episode of Hotel del Luna was watched by an estimated 3,340,000 people.

While the media focuses on the nationwide ratings in their reports of the dramas’ viewership performance, Nielsen provides additional useful information—number of viewers, ratings in Seoul and other cities, ratings for a particular demographic (e.g. 20 to 49 age group)—that are only directly accessible by its clients (broadcasters and advertisers).

And one more thing. What is an audience share? Although we have interchangeably used the terms “viewership rating” and “audience share” in our rating reports, the two have actually different meanings for Nielsen. The rating is the percentage of the total households in the representative sample watching a program, while the share is the percentage of how many homes using TV are watching the program. For example, if Hotel del Luna‘s August 18 episode (broadcast between 9 and 10:30 p.m. KST) got a share of 15 percent, that means 15% of the households using TV from 9 to 10:30 in the evening were watching the drama. This number eliminates those households whose TVs are turned off during the said period, so the share will always be higher than the rating. Unlike in the US, TV audience shares are rarely reported by the media in South Korea.

How are K-drama ratings measured?

Two companies measure TV audience in South Korea—Nielsen Korea and TNmS—but the former is the one that is almost always mentioned in Korean drama news articles about ratings. But, how do they get those numbers?

For Nielsen, it’s a complicated process that starts with a (1) basic survey to accurately understand the TV viewing environment. Based on this survey, the company will (2) select the households that will be included in the representative sample. To avoid bias and minimize the error in the results, the company will see to it that this sample would actually reflect the viewing habits of the entire population by considering several factors including household location, monthly income, no. of family members, their age, and gender.

What follows after the household selection is the (3) installation of electronic measuring devices (a.k.a People Meter) that will record the program or TV channel viewers are watching on each TV at a particular time. Nielsen already completed the first three steps several years ago, but it repeats these steps whenever new households have to be added to the sample.

The set of data collected by the measuring devices is (4) sent every day to Nielsen’s headquarters, where the data from all households are consolidated into a central database. (5) The analyses of all the available information for the past day then take place. During this step, erroneous data are filtered out and other adjustments are made to ensure the accuracy of results. 

After analyzing those data, Nielsen makes its daily TV audience reports available to its clients. News outlets publish the ratings at around 6 am Korean Standard Time every day.

Terrestrial versus cable drama Ratings

Have you ever noticed that terrestrial dramas tend to obtain TV ratings that are higher than what their cable counterparts get? That observation is correct, but it does NOT necessarily mean that terrestrial dramas are more popular than cable series among TV audience. This is because the ratings of the two are derived from different subsets or subgroups of the representative samples.

For terrestrial dramas, the ratings are computed relative only to the households with access to free-to-air TV channels, namely KBS1, KBS2, MBC, SBS, and EBS. On the other hand, ratings for cable dramas are calculated relative only to the households with subscriptions to paid TV channels. Since there are more channels and shows available to cable TV equipped households than their terrestrial counterparts, the competition is more difficult to beat in the former group. As a result, terrestrial TV programs tend to get higher ratings than cable programs do, which is why we cannot directly compare the ratings between terrestrial and cable dramas. But if you really want to determine if terrestrial drama X is more popular than cable drama Y, look at their number of viewers, NOT their ratings.

For example, let us look at the August 29 nationwide ratings of MBC’s Rookie Historian Goo Hae-ryung (terrestrial) and OCN’s Class of Lies (cable). Rookie Historian got a 4.4 percent rating for its 27th episode while Class of Lies recorded 3.5 percent for its 14th episode. Clearly, Rookie Historian‘s rating is higher than that of Class Of Lies. But, is Rookie Historian really the winner between the two as far as TV audience (and by extension, popularity) is concerned? Nope.

Data from Nielsen Korea reveal that Rookie Historian‘s 27th episode pulled in 798,000 viewers, which is lower than the 826,000 viewers who watched Class of Lies‘ 14th episode. Class of Lies also beat Justice‘s 27th episode, which had only 749,000 viewers despite getting a 5.7 percent rating.

Now, how do we know if a drama’s ratings are doing OK or not? What can be considered an “average rating” for a series? Viewership data from 2016 to 2018 can help us set the benchmarks.

Benchmark for Average Ratings of K-dramas

The table above shows that the overall average rating of terrestrial dramas has been dropping since 2016, but if we consider all the series from 2016 to 2018, we can say that a show is doing OK or averagely in terms of TV rating performance if it is getting a number between 6 and 8 percent. A drama’s rating can be described as “below-average” and “above-average” if it is less than 6 percent and more than 8 percent, respectively. In cable dramas, the benchmark for what can be considered an “average rating” stands at 2-4 percent.

Here are some notable examples of terrestrial dramas with below-average, average, and above-average performance in TV ratings:

For cable dramas:

Looking at the said benchmarks, we can say that Hotel del Luna‘s rating performance is at least twice as good as that of an “averagely-rated” cable drama.

Use of Korean drama ratings

In essence, ratings of K-dramas and all other TV programs serve mainly the business interest of broadcasters and advertisers. They help broadcasters determine the right price of their ad inventories at specific time slots. Meanwhile, advertisers can use these numbers to determine where and when to put their ads to maximize target audience reach.

Ratings may also be useful to the ordinary viewers, particularly the international fans of K-dramas, as they tell us which series are popular among the Korean audience. If you’re the type who watches only the popular series, ratings are your best friend at times when you have to decide what dramas to watch.

K-drama ratings on Kdramapal

Korean drama ratings are one of our staple content here on KDP, so have a look at some of our popular posts and pages about ratings:


InternJang manages a team of writers to publish and promote content for Kdramapal every day. He began watching Korean dramas in 2014 and fell in love deeply with his all-time favorites Signal, Reply 1988, and Misaeng. His affinity for writing led him to start a blog and, later on, spearhead efforts to establish KDP as one of the most dependable sources of K-drama information online.

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.