Upon release, the first game was seen as an unexpected hit, earning over US$45 million with about 1.5 million copies sold.[163][164][165] Guitar Hero II was significantly more financially successful, with over 1.3 million copies sold and sales over US$200 million.[163][166] Guitar Hero III, according to Activision, was the first single video game to sell more than US$1 billion at retail, with nearly 3.5 million copies sold during the first seven months of 2008.[167][168] World Tour continued the series' high sales records with 3.4 million units sold in the United States during 2008.[169] More than 60 million downloadable tracks have been purchased across the series as of February 2010.[8] Both Guitar Hero III and World Tour were listed on a March 2011 list from the NPD Group of top-grossing games in unadjusted sales in the United States since 1995; Guitar Hero III tops the list with total sales of $830.9 million.[170]