A phylogenetic network of late-night US television shows

"Late night" broadcasting on United States network / cable TV starts at about 11:00 or 11:30 pm, and goes for a couple of hours. Many networks broadcast similar shows during this time, which directly compete against each other for the available audience (which is currently estimated to be slightly in excess of 10 million people per night at 11:30 pm). Many of these shows have been on for a long time. Most of them are recorded on several weekday nights in front of a live audience, and they are usually associated with only a very few presenters over time (almost always men!).

For example, since the early 1990s we have had:

NBC Tonight Show NBC Late Night CBS Late Show CBS Late Late Show ABC Kimmel Live ABC Nightline ComedyCentral Daily Show ComedyCentral Colbert Report TBS Conan

11:35-12:35 12:35-01:35 11:35-12:35 12:35-01:35 11:35-12:35 12:35-01:05 11:00-11:30 11:30-12:00 11:00-12:00

Jay Leno 1992-2009 Conan O'Brien 2009-2010 Jay Leno 2010-2014 Jimmy Fallon 2014- David Letterman 1982-1993 Conan O'Brien 1993-2009 Jimmy Fallon 2009-2014 Seth Meyers 2014- David Letterman 1993-2015 Tom Snyder 1995-1999 Craig Kilborn 1999-2004 Craig Ferguson 2005-2014 James Corden 2015- Jimmy Kimmel 2003- Ted Koppel 1980-2005 Three-anchor team 2005- Craig Kilborn 1996-1998 Jon Stewart 1999- Stephen Colbert 2005-2014 Conan O'Brien 2010-

Eventually, the presenters retire or move elsewhere, and the other presenters then move around among the shows. This has lead to the so-called "Late night wars", in which the NBC studio executives in charge repeatedly show that their personnel management skills are often lacking. For example, David Letterman was expected to replace Johnny Carson when he retired as the host of the NBC Tonight Show in 1992, but the job was given to Jay Leno, instead. So, Letterman moved to a directly competing show on CBS. When Leno subsequently moved to another show, Conan O'Brien took over. However, Leno then moved back again, and so O'Brien moved to a directly competing show on TBS. The media interest in these shenanigans exceeded their interest in the shows themselves.

Another substantial decision was that by ABC, at the end of 2012, to swap the timelsots of Nightline (which used to run 11:35-12:00) and Kimmel Live (which ran 12:00-13:00). This had a notable effect on the audience numbers, because Nightline was one of the top two shows in its original timeslot whereas Kimmel Live currently gets about 1 million viewers fewer per night in that same slot. On the other hand Nightline in its new timelsot gets about the same audience as Kimmel Live did when it occupied the slot. That seems to be a net loss of audience for ABC.

The Nielsen Media Research viewing data are available online at the TV by the Numbers site. They provide the weekly averages for each show in millions of viewers, based on what is known as "live plus same day" viewing (ie. the audience at the time of broadcast plus same-day viewing of video recordings). The data I have looked at run from early December 2011 to the end of December 2014 (161 weeks). Unfortunately, these data rely on NBC press releases (rather than direct access to Nielsen), so there are some missing data.

The comparison of these shows can be visualized using a phylogenetic network, as a tool for exploratory data analysis. To create the network, I first calculated the similarity of the nine shows using the manhattan distance; and a Neighbor-net analysis was then used to display the between-show similarities as a phylogenetic network. So, shows that are closely connected in the network are similar to each other based on their audience figures across the three years, and those that are further apart are progressively more different from each other.

The network shows a gradient of increasing audience size, from bottom-left to top-right. So, the Tonight Show consistently got a average nightly audience of c. 3.5 million people, while Conan had c. 0.8 million. The two CBS shows both consistently did somewhat worse than their NBC timeslot competitors.

The two ABC shows apparently did well, but this is confounded by the timeslot swap noted above. Nightline did well for the first year (before it was moved) but not for the second two years, while Kimmel Live did the opposite. This is what creates the big reticulation in the middle of the network, as all of the other shows had fairly consistent audiences throughout the three years.

However, there was a steady decrease in the total audience size across the three years, from c. 12 million per night (at 11:30 pm) at the end of 2011 to c. 10 million at the end of 2014. The only major exception to this was at the time when Jimmy Fallon took over from Jay Leno (early 2014). For several weeks the Tonight Show audience increased to >8 million per night, so that the total audience was c. 15.5 million (a 50% increase). This shows just how many people are available to be added to the late-night viewing, compared to how many watch regularly. So, why are they not watching in the other weeks? It seems that Late Night Television is not reaching its full potential.