In the first quarter of 2007, there were a total of 3,625,639 background checks done.
The first quarter of this year,2013, there were a total of 8,728,673 background checks done.
That's an increase of 5,103,034 in checks during the same months, in each respective year.
In 2012, the total number of background checks by NICS totaled 19,592,303 checks. An increase of more than 3 million over the previous year. In 2007 the total number was 11,177,335.
This post was edited on 5/12 at 2:18 pm