Friday, February 01, 2008

The Digg Heat Map

After my post about the number of registered Digg users got picked up by bloggers (Cliff Notes: 2.7m registered users, about 19% have been banned) I took at look at the information available through the Digg API.

The API has and end point to get user information (in chunks of up to 100 users) and that user information includes the date and time of registration to the nearest second (along with the user's name and icon and number of profile views).

So I wrote up a little script and used it to pull down information on 100,000 Digg users so that I could look at the pattern in registration times. I was specifically looking to see if there was evidence that Digg's audience is based in a certain geography, or that the geography had changed over time.

To make sure that I had a good spread of data I plotted the chart of signups over time for comparison with the chart I generated for my previous blog post. Comparing the two it looks like I have good coverage of the life of Digg:

I then plotted the registration times from the Digg API on a simple heat map: the x-axis is the hour during the day that the user registered (US West Coast time) and the y-axis is the month and year. Here's the map:

The brighter the red, the more people signed up during that hour. Note that brightness is calculated on a per-row basis so that although the number of users has increased each row is considered on the same scale (0-255).

In 2004 Digg was really only just starting and the early developers were clearly not morning people :-)

It's very obvious looking at this that Digg's audience has not changed geographically greatly since 2005. There's a strong band of signups between 0600 and 1500 US West Coast time. That indicates to me that Digg's audience is overwhelmingly US based.

If you consider the 4 US time zones, and imagine people are working between 0900 and 1800 (most web surfing is done at work) then it's easy to draw a little chart that shows when you'd expect the peak to be. The following chart shows the number of US time zones that are working relative to US West Coast time:

That corresponds very nicely to the hot zone of Digg registrations.

It's also obvious the US registrations vastly outweigh UK and European. The UK is 8 hours ahead of the US West Coast, and most of Europe is 9. So at midnight in California it's 0800 in the UK and 0900 in Europe. Looking at the blackness of night in the heat chart indicates that there aren't that many European Digg users.

So, my summary is that I think Digg remains mostly a US phenomenon with most of the users signing up while at work.

Thank you Digg for providing such a nice API. And if anyone else has suggestions for data I can poke at, please email me.


If you enjoyed this blog post, you might enjoy my travel book for people interested in science and technology: The Geek Atlas. Signed copies of The Geek Atlas are available.


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