Update May 20: Updated the podcast list at the bottom of the post.
Update May 29: Updated the podcast list again. Tell me if I’m missing any.
This is the first of what I hope will be a series of posts on measuring skepticism’s digital footprint. Skeptics often talk about our outreach and effect, but how can we know what that is unless we are measuring our efforts? Fortunately, measuring things online is pretty straightforward. So I set out to generate some basic measurements of the content skeptics are generating online. In this post I will tackle podcasts.
Skeptical podcasts began six years ago this month, when both Skepticality and The Skeptics’ Guide to the Universe posted their first episodes in May 2005. They were eventually followed by a number of other podcasts. In my fairly unscientific survey, I was able to locate about 50 skeptic podcasts, or science podcasts which sometimes feature skeptic content. Some are still generating content, but a few are now defunct.
Fortunately for this project, it has become standard practice for free podcasts to include their entire past episode catalog in their podcast feed. This is so new listeners can easily access the back catalog at will. But it also means that the episode titles, publication dates and (in most cases) the duration of the episodes are present right there in the feed. So without downloading a single audio file, all the information we need is readily available.
I manually surveyed iTunes and other catalogs for skeptic podcasts, and came up with about 60 of them. See the bottom of this post for the full list.
I deliberately avoided including podcasts that primarily contain atheism, secularism or humanism content, and not much science. This was admittedly arbitrary, as I don’t listen to many of these and therefore are less familiar with what is out there. But I was also trying to keep the project from becoming unwieldy in size. If someone out there would like to repeat my methodology for atheist podcasting, I’ll be glad to share the scripts I used. (I did, however, include a few podcasts that are primarily science content but occasionally inject skepticism, see the list).
As is usual for this sort of thing, I ran into various difficulties in particular cases. Not every feed includes the aforementioned <itunes:duration> tag, which means the episode lengths had to be estimated based on the file size of the enclosure. (i.e. the <enclosure length=> tags in the feed). This calculation had to be customized on a show-by-show basis based on the audio quality. I did this manually as needed.
Still other podcasts post their audio enclosures with no length attribute at all! In these cases the actual length of a few representative episodes was determined by manually downloading them, and the average for that show was used as a default.
Finally, some podcasts actually do not list their entire back catalog in their feed. (Instead, they list only the last few episodes. This is fairly standard for blogs, but unusual for podcasts). This affected about one quarter of the shows (15 of 62). Those programs will be under-represented in the historical data but their data should be accurate for 2011. (In a future update of this survey I may look into adding their back catalogs by hand).
Bottom line: the numbers in the results are definitely an undercount to some degree, and definitely just an estimate.
The output of my script was a simple set of comma-separated values. This CSV data was then imported to a spreadsheet program to generate the results and charts.
Once compiled, the data included 3,197 podcast episodes that dated from April 2005 to May 18, 2011. The total length of all the episodes is over 97 days. So if a new skeptic starting from scratch wanted to listen to every episode, it would take over three months of 24 hour a day listening.
The average length of each episode varies a bit from year to year, but is basically right around 45 minutes. I’ve not seen a strong consensus on what constitutes an “ideal” podcast episode length, but I suspect some would argue this is on the long side for most podcasts.
In the first year of skeptic podcasting, 76 episodes were produced. In 2010 skeptics produced over 13 times that – 1,011 individual episodes.
Growth has been strong and continuous throughout the 6 years, but there was a definite surge during 2009 (almost 70% growth over 2008). It may not be obvious from the graphs, but the growth seems to be tailing off this year. Instead of the 40% to 70% increases of past years, my projections indicate there will only be 10% growth in skeptic podcasting this year. I have no explanation for this.
One of the questions I wanted to answer was: is it even possible for a skeptic to keep up? In other words, can you listen to every single episode of every skeptic podcast and not fall behind? To answer that, I calculated the total length of new episodes being produced on a daily basis. That’s the second chart.
In 2005 a commitment of 13 minutes per day would be required to hear everything. That nearly doubled in 2006. By 2010 that had grown by almost an order of magnitude to 2 hours, 3 minutes. So far in 2011, skeptical podcast output amounts to 2 hours, 16 minutes per day.
I think the answer to my hypothetical question is: no, it is no longer possible to listen to everything, though it once was.
Here is my list of podcasts. The 56 that are not in bold were included in my survey. Some are already defunct, I included them to so that the year-to-year comparisons would be as realistic as possible. Feel free to point out any errors or omissions in the comments, I’ll remedy them in future revisits to this survey. (I will admit there are a few obscure now-defunct shows that only had a handful of episodes that I skipped out of sheer laziness).
The podcasts listed in bold were added after the first version of this article, but are not included in the data above. The pocasts marked with an asterisk (*) after do not list all their episodes in their RSS feed and are thus under-represented in the historical data.