That is what they wrote on their site. I think they have forgotten to add that is is a really wonderful mail project.
The project:Each week we collect and measure a particular type of data about our lives, use this data to make a drawing on a postcard-sized sheet of paper, and then drop the postcard in an English “postbox” (Stefanie) or an American “mailbox” (Giorgia)!
We’ve also noticed that the data collection and visualization process has become a sort of performance and ritual in our lives, affecting our days and weeks, and inherently changing our behaviour. [...]
But really, we also started this project to show how “data” is not scary, is not necessarily “big”, and that you need to know almost nothing about data to start collecting and representing it (just a pencil, a notebook and a postcard!).