Los Angeles - Home of the cheap 11AM quickie

Cause I’m a data whore

Following Plenty Of Stats, I got some suggestions for expanding the vice tracking of certain cities. In particular, Loren Norman pointed me to an article that tried to gauge prostitution levels in each major city by their “erotic services” postings on Craigslist.

Now the article didn’t give any details about how they actually calculated the data other than to say that “a high number of prostitutes advertising openly on Craigslist suggests lax enforcement in that area”. There are a lot of factors that have to be considered here. First being the size of the city being tested and secondly, the Craigslist popularity in that city. For example, it could be expected that San Francisco would have a higher percentage of Craigslist users per capita due to its wired nature. And you can’t compare Atlanta to New York.

The method behind the madness

So we need a baseline. The best I could come up with was the Housing category - the whole thing. Cities with a higher usage rate or larger population won’t be penalized, and less wired towns should reflect a lower usage in both categories.

I pulled the XML feeds of both Housing and Erotic Services, frequently throughout the day for several days in a row and tallied up the results.

What we are asking is simply “For every 100 Housing posts, how many ‘Erotic Services’ posts are there?”

And the data say:

Taking a further look at LA:

What did we learn?

  1. Prostitutes keep pretty regular hours. The workday for prostitutes seems to start at around 9AM. I like to wake up at 7AM. That makes me feel good about myself.

  2. If you in the market for ‘erotic services’ in LA, it means you’ll probably strike a better deal at 11AM. If they’re posting ads with such fervor at 11, it’s a good bet that they’re not umm… providing services. So get there before lunch and save!

  3. LA is a dirty dirty town, while Boston is suprisingly “un-prostituty” for such a large city. What, are you guys too good for prostitutes?

On a more serious note, it’s interesting to see such swings in usage. You have large towns that swing from the extremes of LA to the lows of Boston. The question we can’t answer is why. But one could guess that it comes down to enforcement. Does the city of Boston tackle online prostitution, while cities like Atlanta tend to overlook it? Or is there some other factor at play going on here. Feel free to hit me up on twitter about it @markpercival or @webchicanery.

Just some quick notes:

  • I took a sample every 15 minutes of Craigslist posts for 3 days in all the major cities.
  • Rather than tracking all the posts, I used a measure of velocity at the moment the sample was taken. This way I only have to pull the default 100 most recent posts. For example - the oldest post in the 100 most recent is 2 hours old, this means the velocity of posting at the current moment is 50 posts per hour, or 1200 a day.

And yes, I did just show you the cheapest time to buy a prostitute using a combination of Ruby programming, SQL, and an excel spreadsheet.