AT TWENTY-THREE minutes past one in the morning of April 26th 1986, a safety test at a nuclear reactor in Soviet Ukraine went catastrophically wrong. The resulting steam explosion at the plant near the city of Pripyat, 70 miles north of Kiev, spewed out so much radiation that much of the surrounding area will be uninhabitable for 20,000 years. Harmful isotopes were carried by the winds as far as Ireland within a week. According to some accounts, first responders who were exposed to large doses of radiation suffered agonising deaths. These events, as well as the political intrigue of the Soviet government’s actions, are the subject of HBO’s historical drama series, “Chernobyl”. Following the final episode, which aired in America on June 3rd, it is the highest-rated television series of all time, according to crowd-sourced reviews on IMDb, a film and television rating site.

Reviewers have given the miniseries stellar ratings. A weighted average of all five episodes calculated by The Economist (according to how recently each episode ran and the number of reviews) accords it 9.7 points out of 10. By the same measure, other leading shows—including comparable historical drama series such as “The Crown” and “The People v. O. J. Simpson” (now called “American Crime Story”)—lag behind.

What is more, every episode of “Chernobyl” has been rated by IMDb users at 9.5 or higher, a unique streak. According to The Economist’s analysis of 518 episodes of popular television dramas, the likelihood that any show would produce even four consecutive episodes that each score a 9.5 or above is roughly 0.4%. Apart from “Chernobyl”, only the final four episodes of “Breaking Bad”—previously the highest-rated show—had accomplished this feat.

All of this is even more impressive given its subject matter. Documentaries typically struggle to gain as much attention as action and fantasy shows such as “Game of Thrones”, and the same is true of historical dramas. Even series about well-known subjects, such as Queen Elizabeth II or the trial of O.J. Simpson, earn user ratings that are typically below those of the most popular shows. In comparison, “Chernobyl” scores better than the greats.

The show has also caused a massive spike in interest about the actual disaster. Web traffic to the entry for the Chernobyl nuclear disaster on Wikipedia, an online encyclopedia, has increased 56-fold since the start of the year. Interest in a comparable nuclear disaster at Japan’s Fukushima Daiichi power plant in 2011 has also increased, though by a more modest 21 times.

Editor’s note (June 4th 2019): This piece was originally published on June 3rd and has been updated following the airing of the final episode in America. IMDb reviewers gave it a rating of 9.9 out of ten.