ON SEPTEMBER 22nd 18m Americans huddled around their televisions to find out the fate of Leroy Jethro Gibbs, the silver-haired, stoic lead of “NCIS”. Although you would never know it from the newspapers, “NCIS” (which stands for Naval Criminal Investigative Service), is America’s most-watched television drama. Combining the elements of a police procedural with an extra splash of ooh-rah patriotism, the show appeals to America’s heartland but repels big-city liberals. With a median viewer age of 61, it’s the least hip show on television.

Shows like “NCIS” and “The Big Bang Theory” (the most-watched show overall) illustrate a growing divergence in the television-viewing habits of coastal urbanites and the rest of the country. Both shows are produced by CBS, have huge followings—averaging over 20m viewers each—but receive very little attention from the media. In contrast, critically-acclaimed shows like “Game of Thrones” and “Mad Men” each averaged just 9.3m, and 3.7m viewers, according to Nielsen, a television-ratings agency. Since "Mad Men"’s launch in 2007, The New York Times has written 2,480 articles referencing the show, but just 231 mentioning “NCIS”, despite the latter sharing its name with two popular spin-offs (NCIS: Los Angeles and NCIS: New Orleans) and a federal agency. There appears to be minimal overlap in what shows are watched by most people compared to the cultural elite [see chart below].

While data on viewership by region aren’t readily available, a quick look at Google searches by geography can offer some valuable insights into the split between the big liberal cities and the rest of the country. “Game of Thrones” has generated more buzz on the internet than “NCIS” all across America, but there are noticeable regional differences in taste. In the New York City metropolitan area, searches for “Game of Thrones” dwarfed searches for “NCIS” nearly six-to-one; in Sioux City, South Dakota, the ratio is two-to-one.

A reason for this dissonance is the emergence of pricey premium television channels like HBO, which produce quality content but have a far smaller reach. Historically, all Americans watched the same shows. From the 1950s until the late 1990s, the big four broadcast networks (ABC, CBS, NBC and FOX) dominated American television, both in terms of viewership and prestige, between them capturing nearly all Emmy nominations. A crack in the facade first emerged in 1999, when "The Sopranos", produced by the premium network HBO, started making waves on the red carpet. Since then, the big four have only continued to lose ground to the smaller, nimbler premium channels. During this year’s Emmy awards ceremony, none of the shows produced by the big four networks were nominated for best drama.

The rise in online streaming services like Netflix has only added to the traditional networks' woes. A recent Nielsen report notes that half of the households in New York and Washington subscribe to a streaming service compared to just a third in cities like Cleveland and Pittsburgh, partly explaining why the tastes of TV critics seem to differ from those of the rest of the country. For those living in rural areas with shoddy internet connections, award-winning, online-only shows like "House of Cards" may be entirely out of reach.

The golden age of television has elevated the boob-tube to a first-tier medium, but it hasn’t quite reached everyone. At the height of its popularity in 1953, two-thirds of television-owning households tuned in to “I Love Lucy”; “NCIS” attracts just 13%. America will never again be so united in its television viewing.