In an effort to better understand the patterns within the 2008 presidential candidate donations, the authors produced this interesting diagram, mapping all donations made between January 2007 and July 2008, to McCain (left in red) and Obama (right in blue). The two inner circles represent the total amount of donations for both candidates, while the outer segments illustrate variations in the amounts donated. The top-most bracket is any donation between $1 and $100, the second: $101 - $500, the third: $501 - $,1000 and the final: all amounts over $1,000. The size of each bracket represents the percentage amount that bracket constitutes in a candidate's total donations, and the hair-like lines coming out of them are the names of each donor, which produces a useful visual reference to the density of each category.
The distinction between candidates is immediately perceived with this visualization. As the authors explain: "What is most striking to us is how much more of Obama's donations come from the $1 to $100 bracket. We found a high number of students, artists, unemployed and self-employed people who fell in this bracket. One can speculate that these are the younger-generation individuals who will be voting for the first time or they are a struggling class of lower income workers. Probably more significant: this shows how much internet contributions have helped the Obama campaign, assuming the smaller amounts were made online. This data also shows that a majority of McCain's donations come from the $500 to $1000 bracket of donors. The amount is still smaller than Obama's, but this makes up almost two-thirds of his donations".
Since the donation information must be disclosed to the public, the authors turned to the Federal Election Commission to find a data set containing all donors, the amount they donated as well as other information they may explore in the future (e.g. occupation, zip code, employer). The data set time span is currently from January, 2007 through July, 2008, but the authors will be updating this information every month, as new data is released.