5/30/2013: Article published at PLoS ONE; added article link and Twitter feed @geographyofhapp to main index page.
3/28/2013: Removed all instances of the capitalized string "HI" from the data set; changed happiness score for Hawaii to 6.16; updated Hawaii word shift graphs. Thanks to anonymous PLoS ONE reviewer for suggesting this.
2/28/2013: Removed all instances of "battle" from the data set; changes happiness score for Battle Creek to 5.99; updated word shift graphs. Thanks to Stephen for spotting this.
2/19/2013: Corrected lists of top 5 happiest and saddest states in Figure 1. Thanks to @tophtucker for noticing this.