This visualization is a linked treemap (bottom) and line chart (top right). The treemap uses area to show the relative proportions of a whole, in this case all the students who applied or were accepted to a UK university in the given year. The line chart shows how much the currently selected group has grown, relative to the indicated year. (For instance, if 2003 is the reference year, mousing over the 25 to 39 year old female treemap cell will show that the group is twice the size (that is, a 100% gain) in 2010 as it was in 2003.)
This visualization uses the 2003–2010 "Ethnicity / Social Class" data from UCAS. They provide the data in executable self-unzipping Excel sheets, but we wrote and open-sourced a script to normalize and import into SQLite.
This visualization was made for Postgrad.com & David McCandless's Data Visualization Competition by Kevin Lynagh of Keming Labs the weekend of 2011 June 10. Thanks to Mike Bostock for d3.js and Jeremy Ashkenas for CoffeeScript. Also thanks to the fine people at Periscopic for helpful UI advice.