In March 2011, I came across a Data Viz competition sponsored by Google and Eyebeam, an art and technology center. The idea of the competition was to find a way to visualize the federal budget so people could better understand where their tax dollars go. I love data visualizations, but I wanted to challenge myself and my teammate to come up with a concept that had more visual dimension rather than more standard flat aesthetic used for data visualizations. We came up with the idea of a pie chart that could represent positive as well as negative numbers.
How do you represent negatives on a pie chart? With depth. Each piece of the pie chart is accurately represented in area and in depth. Negative numbers are represented by a depth that dips below the baseline. Some of the features we included are: a snapshot history of where you've explored, a way to compare your two budgets over time, a filtering system, and a way to drill deep down into the chart.
My teammate and I took home an honorable mention in the competition.