Porn is one of the biggest yet worst-covered topics in popular discourse. It’s a multi-billion dollar industry that sits at the heart of human sexuality in the 21st century. Many people watch it, though few talk about it, and for better or worse it exerts a major influence over our culture; but we know relatively little about it.



What if we could find some big source of data? The website Clips4Sale.com is one of the leading commercial porn sites on the web. It’s home to thousands of studio selling millions of clips. All the clips are indexed with metadata about their price, file size, fetish category, length, title, description and so on, and the site’s permissive robots policy allows web crawlers to trawl the content. How much useful information could you dig out from it? What interesting things could you find?

The other weekend I wrote a script to find out. It crawled the site gathering data on 4,814,732 clips, which is rather a lot of porn and probably means I’m on some BT blacklist now. The earliest clips date back to late 2003, which makes the Clips4Sale corpus a 12-year history of paid porn on the Internet. Each month’s data is like a ring in a tree trunk, telling us what the market was like at that time. It’s not perfect – older clips may have disappeared or been deleted – but it’s enough to give us a rough picture.

The earliest clips are grouped in a handful of categories with names Asian, Foot Fetish, Tickling and Amateur, but the number of fetishes covered grew rapidly. By 2005, there were more than 100 active categories in any given month. By 2010 that number had reached 500. In March 2015 content was posted in almost 900 categories, and the site continues to gain breadth. In total, over 946 fetishes existed on the site at the time of my scan, from 1920s Porn to Zit Squeezing, and the number continues to grow.

Growth in categories over time.

The clip count is growing too, with the site gaining nearly 80,000 clips per month this year. I’m sure climate skeptics will want to focus on the unusual October 2014 reading and argue that porn is now in decline, but the inconvenient truth is it seems to be growing faster than ever. By this time next year another million clips will have been uploaded.



The growth in clips per month over the last decade.

(What’s slightly weird about that chart is the flat period between 2009 and 2011. If I didn’t know better I’d start hand-waving about the global recession hitting around the same time, but I do so I won’t. It could just be a coincidence, or an artefact of some sort in the data.)

Things get a bit more interesting when it comes to pricing. The next chart shows the average price per clip. In the early days it goes all over the place (and remember there are very few clips back then), but as the site matures the market stabilises and you see a pretty clear long-term trend. In 2005 the average price is a little over $8 per clip, and by March 2015 it’s somewhere around $9.70.

Average clip price, 2003-2015.

There’s a site called the US Inflation Calculator that allows you to enter two dates, and adjust prices for the amount of inflation that occurred between them. Entering the figures, it turns out that an item that cost $8.10 in the United States in 2005 would cost $9.79 today. In other words, porn prices have almost exactly tracked inflation.

Or have they? Twist ahoy!

It turns out that price isn’t the only thing getting bigger in porn… lengths are too, and I’m not talking about the performers (that data wasn’t available, sadly). The average clip has swollen from a respectable eight minutes to an eye-watering nine-and-a-half over the last decade, while the price per minute has risen from $1.15 to $1.25. If we adjust the 2015 figure for inflation, prices have actually dropped in 2005 dollars from $1.15 to $1.03.



Average length in minutes, 2003-2015.

Average price per minute, 2003-2015

So while the overall cost per clip has kept pace with inflation, producers have had to pack more content into each clip - you literally get more porn for your dollar now. Of course that goes for megapixels too. The average file size has gone up from about 60 megabytes a decade ago to over 250 today, in the HD era.

Average file size (MB), 2003-2015

Even when you look at specialty fetishes with unusual production demands, the price still holds at around a dollar a minute. Giantess Special Effects clips, which make heavy use of blue screen effects, animation and post-production, actually cost about ten cents less per minute than conventional Giantess clips, for example. The Animation category is a little more expensive than average, but only by a few cents.

The picture this paints for the porn industry isn’t exactly a healthy one. Amateurs flooding the market have kept prices low. It’s true that producers have benefitted from billing systems, cheaper equipment, bigger potential audiences and so on, but at the same time they’re trapped in a relentless squeeze.

So far we’ve looked at all clips together, but it turns out that not all fetishes are equal. One of the starkest differences is between the BDSM and Foot Fetish categories. BDSM clips in the last few months have averaged around $1.10 per minute, whereas Foot Fetish videos have been over $1.20 for a while now, but that pales in comparison to the difference in length – BDSM clips average around 11-12 minutes, but Foot Fetishists have to make do with clips averaging barely 7 or 8 minutes.

So why is that? Is it to do with the nature of the fantasy and the scenarios involved? Do BDSM scripts with a deeper psychological element require more time, exposition or setup to pull off? Does it take less time for foot fetishists to achieve orgasm, leading to a preference for shorter clips? Who knows, but it’d be interesting to investigate further, and if anyone has any insights do get in touch.

Let’s explore fetish-space some more, starting with the Top 40 most popular list:

BONDAGE

FEMALE DOMINATION

FOOT FETISH

TICKLING

FACE SITTING

SMOKING

HANDJOBS

FOOT WORSHIP

BLOW JOBS

TRAMPLING

MASTURBATION INSTRUCTION

FOOTJOBS

BALLBUSTING

PANTYHOSE/STOCKINGS

FARTING

FOOT DOMINATION

AMATEUR

18 & 19 YRS OLD

BALLOONS

MILF

HUMILIATION

MIXED WRESTLING

LESBIAN

INTERRACIAL

MASTURBATION

CBT

HIGH HEELS

SUPERHEROINES

CAT FIGHTING

BIG TITS

BDSM

SPANKING

PANTY FETISH

GIANTESS

PEDAL PUMPING

ASS WORSHIP

ANAL

FEMALE WRESTLING

STRAP-ON FEMALE TRAINING

This list isn’t a brilliant one because the categories have changed and evolved over time and they’re pretty loosely enforced. Larger categories are prone to being split up, to make them easier to search. This leads to some pretty confusing and misleading results: Bondage and BDSM are in separate categories for example, while Rope Play would easily be in the Top 10 if you included all the clips that mention the phrase but are actually under Bondage. Still, there’s some interesting stuff here. It turns out that a lot of seemingly obscure kinks are way more popular than you might expect. Okay maybe not Big Tits, but the popularity of the Pedal-Pumping, Giantess, Balloons and Smoking fetishes was a bit of a surprise to me.

It’s hard to do the same kind of list for pricing because it turns out that expense is itself a fetish. The top three most expensive categories are therefore Ripoff, Money Fetish and Financial Domination. One other trend was clear though – clips aimed at gay men are a long way down the rankings. None of the dozen or so gay porn categories ranked in the top half, with Gay itself languishing in 730th place, with an average price of only $1.05 per minute.

Can we link these fetishes together in some way, to create some kind of map of human sexuality? To find out, I looked for fetishes that frequently appeared together in the same studios. Having built up a table of links I filtered out the weakest candidates, loaded it all into JUNG (a Java library for graph visualisation), and applied a simple clustering algorithm to it that grouped fetishes according to the number of connections within the group.

It’s the least scientific part of an already pretty unscientific article, and 2D representations of complex spaces are never particularly accurate, but I wanted to get a suck-it-and-see picture showing roughly what fetish-space looks like. The result is the closest thing I’ve ever seen to a real, data-driven map of human sexuality, and while it’s heavily flawed it’s still quite fascinating.

An attempt to visualise ‘fetish space’, generated from connections between fetishes that commonly appear in the same Clips4Sale studios. Links connect fetishes that frequently appear together in the same studios, and larger circles represent categories with more clips (from a handful to over 100,000).

You can explore the image at your leisure, but in the meantime here are a few noteworthy clusters:

A set of categories aiming to promoting greater age diversity among women performers. Maybe.

The size fetish cluster (right) is one of a few to feature categories from both ‘straight’ (Giantess) and ‘gay’ (Giant) porn.

No fetish is too obscure to have a category, or indeed a sub-category.

A group of categories inspired by the US record industry.

So what can we take away from this? Well potentially lots of things, but this isn’t really intended to be an in-depth analysis, just me pottering about for a bit of fun. There’s really only one concrete conclusion I want to make, and it’s this: there is a vast ocean of data on the web about human sexuality, far more than I think people realise, and it could be an enormously valuable tool in developing our understanding of a really important topic.

In the space of a couple of weekends I was able to cobble together some code and come up with some interesting findings. A good researcher in the field can do far better, and I hope they do. Watch this space...



@mjrobbins

Note 1: I did try to contact Clips4Sale prior to this article, but they weren’t available for comment.

Note 2: If you’re an academic or you work in the porn industry and you’ve got any interesting ideas or you’d like to know more, you can e-mail me at layscience@googlemail.com.