According to the Entertainment Software Association (ESA), during the period 1996–2009, in the United States alone, the number of video games sold for use on a console or personal computer increased from 73.3 million units to 273.5 million (ESA 2010). For the same period, spending on these games rose from 2.6 billion dollars to 10.5 billion (peaking in 2008 at 11.7 billion dollars). Similarly, in the United Kingdom in 2008, video games were reported to have become the UK's most popular form of entertainment, with sales for that year estimated to be around 4.64 billion pounds (Cellan-Jones 2008). Moreover, in its 2010 report, the ESA claimed that 67 per cent of households in the US owned either a gaming console or a personal computer used to run entertainment software, that the average age of a gamer was thirty-four – with 49 per cent aged between eighteen and forty-nine – and that, on average, adult gamers had been playing video games for twelve years. The ESA report also contained a list of the top twenty console games for 2009 (based on units sold). Ranked number one in the US was Call of Duty: Modern Warfare 2 (rated “mature”). In fact, Prigg (2009) reports that 4.7 million copies of this game were sold on its opening day in the US and UK alone, out-selling the previous best video game – Grand Theft Auto IV – by some distance. (Prigg also reports that of the 4.7 million sold, the sale of 1.23 million copies in the UK was a record for that country.)