September 12, 2008

Red Book, Blue Book

Amazon is getting in on the election data visualization game by offering a map of "political" book purchases:
Our 2008 election map colors each state according to the book-buying habits of its residents on during the past 60 days. You can also see how the map has changed over time by using the left and right arrows to choose other two-month periods during 2008, and by clicking the "2004" tab to find maps for the same periods during the last presidential election year.

In recent years, thanks to the color-coded maps the networks use on election night, "red state" has come to represent a state favoring the Republican Party or more conservative beliefs, while "blue state" represents one that favors the Democratic Party or more liberal beliefs. We know that states are not all red or all blue, and readers aren't either. And books are often too complex to fit into such neat categories. But given the high interest we've seen in political books during election years, we thought our customers would like to see what general book buying patterns emerge across the country, and how they change over time.

To calculate each state's red and blue percentages for our map, we have classified books as red or blue if they have a political leaning made evident in book promotion material and customer classification such as tags. To compute our totals, we then use the 250 blue books that have sold the most during the time period and compare those sales against the 250 red books that have sold the most during the same time period. All orders during the period are given equal weighting in the calculation. These lists of red and blue books, along with the state percentages, are updated daily. States with higher percentages of red or blue purchases are colored more darkly, and states with an even 50-50 split are colored yellow. The featured "local favorite" books for each state are the red and blue books whose sales are strongest in that state compared to their sales in other states.

Since not every political book is a red or a blue book, we've also prepared a list of "purple" books that includes journalistic accounts that present themselves as nonpartisan (even though they might be more critical of one party or another), as well as books that cross the usual party lines (even if they might be written by a member of one party or another).
Not nearly as interesting as their old purchase circles data (which are still under perpetual renovation) but mildly amusing I suppose.

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