reported acquiring firearms used in their crimes "At a gun show", with repeat offenders less likely than first-time offenders to report acquiring firearms from a retail source, gun show or flea market. This 2001 study examined data from a 1997 Department of Justice survey of more than 18,000 federal and state prison inmates in 1,409 State prisons and 127 Federal prisons. The remaining 99.2% of inmates reported obtaining firearms from other sources, including "From a friend/family member" (36.8%), "Off the street/from a drug dealer" (20.9%), "From a fence/black market source" (9.6%), "From a pawnshop", "From a flea market", "From the victim", or "In a burglary". 9% of inmates replied "Don't Know/Other" to the question of where they acquired a firearm and 4.4% refused to answer. The Department of Justice did not attempt to verify the firearms reported in the survey or trace them to determine their chain of possession from original retail sale to the time they were transferred to the inmates surveyed (in cases where inmates were not the original retail purchaser). Garen Wintemute, a professor of emergency room medicine and director of UC Davis' Violence Prevention Research Program, released a study in 2007 which held that gun shows are a venue for illegal activity, including straw purchases and unlicensed sales to prohibited individuals. In 2011, economists Mark Duggan and Randi Hjalmarsson at the University of Maryland and Brian Jacob from the University of Michigan released a paper which stated that gun shows do not lead to substantial increases in either gun homicides or gun suicides. ATF criminal investigations at gun shows From 2004 to 2006, ATF conducted surveillance and undercover investigations at 195 gun shows (approximately 2% of all shows). Specific targeting of suspected individuals (77%) resulted in 121 individual arrests and 5,345 firearms seizures. Seventy nine of the 121 ATF operation plans were known suspects previously under investigation. Additionally, ATF Field Offices report that: Between 2002 and 2005, more than 400 guns legally purchased at gun shows from licensed dealers in the city of Richmond, Virginia, were later recovered in connection with criminal activity. Bouchard said, "These figures do not take into account firearms that may have been sold at Richmond area gun shows by unlicensed sellers, as these transactions are more difficult to track." It is noteworthy that the "in connection with criminal activity" category includes stolen guns later recovered from burglaries, but the report does