An analysis of 1,638 game ratings issued by the Entertainment Software Rating Board in 2010 shows over half of the evaluated games received an E (Everyone) rating, with only 5 percent of titles rated M (Mature). Fully 55 percent of ESRB-rated games received an E in 2010, with an additional one percent rated EC (Early Childhood). An E10+ (Everyone 10+) rating was given to 18 percent of 2010 releases, while 21 percent of the titles received a T (Teen) rating. No 2010 titles were rated AO (Adults Only). The breakdown is in line with the previous three years, in which roughly 60 percent of games received an E rating and 6 percent of games were rated M, according to previous ESRB statements. A 2007 Gamasutra analysis of game ratings across systems found that Sony and Microsoft systems include a significantly higher proportion of M- and T-rated games and a lower proportion of E-rated games than Nintendo systems. Though M-rated games make up just a fraction of distinct 2010 titles, such games tend to dominate industry sales. Five of the top 10 selling new retail games in the U.S. in 2010 were rated M, including overall top-seller Call of Duty: Black Ops, which NPD recently named the best-selling game of all time in the U.S. A late 2009 survey commissioned by the ESRB found that 70 percent of U.S. parents consider ESRB ratings when making purchasing decisions for their children. But groups including the Parents Television Council and the FTC have criticized game retailers for lax enforcement of ESRB ratings, saying unaccompanied children were able to buy M-rated games during one out of five secret shopper visits.