Entertainment Software Association (ESA) from the USA has published results from their annual market studies for several years, providing interesting claims and figures about the role of digital play in the American society. The key weakness in these reports is that they do not explicate their methodology, nor do they subject the studies to scientific evaluation and criticism. So: a word of caution while making use of these reports.
ESA (2007) ‘Essential Facts about the Computer and Video Game Industry 2007: Sales, Demographic and Usage Data’. Entertainment Software Association. Online: http://www.theesa.com/facts/pdfs/ESA_EF_2007.pdf
An Introduction to Game Studies 