In a guest post Lorenz Matzat, editor of ZEIT Online’s Open Data Blog, writes about the background to their online app exploring the issues around data retention by mobile phone companies.

It’s not very often that one can follow the direct impact of an article, let alone a piece of data journalism. But the visualization of the cellphone data of Malte Spitz from the Green party in Germany led to visible repercussions in the US.

Following a piece in the New York Times about Spitz and the data app, some days ago two senators wrote a letter to the 4 main US-carriers for information about their data retention policy.

After publishing the app in German one month ago (and 20 days later the English version), the feedback was overhelming. We didn’t think that so many people would be so interested in it. But Twitter and Facebook in Germany went wild with it for some days – along with coverage in many major tech websites.

Probably this is why data journalism works: Making an abstract notion everybody knows about visible: that every position of you, and every connection of your mobile phone does is – or could be – logged. Every call, text message and data connection.

The background

Around February 1st, ZEIT Online asked me if I had an idea what do do with the dataset of Malte Spitz (read the background story about the legal action of Spitz to get the data here). Continue reading →