A background check is initiated when someone starts the process of buying a gun. There is not a one-to-one correspondence between background(bg) checks and gun purchases as a purchaser may buy more than one gun with one bg check. A buyer may trade in one gun when buying a new one. A father transfers a gun to his son and a bg check is performed(yeah, right)
2009 13,984,953 bg checks
2010 14,320,489 bg checks
2011 16,336,732 bg checks
2012 19,463,832 bg checks

70291049 Background Checks Since Obama Took Office