In the years following the passage of the Gun Control Act of 1968, people buying guns were required to show identification and sign a statement affirming that they were not in any of the prohibited categories. Many states enacted background check laws that went beyond the federal requirements. The Brady Handgun Violence Prevention Act passed by Congress in 1993 imposed a waiting period before the purchase of a handgun, giving time for, but not requiring, a background check to be made. The Brady Act also required the establishment of a national system to provide instant criminal background checks, with checks to be done by firearms dealers. The Brady Act only applied to people who bought guns from licensed dealers, whereas felons buy some percentage of their guns from black market sources. Restrictions, such as waiting periods, impose costs and inconveniences on legitimate gun purchasers, such as hunters. A 2000 study found that the implementation of the Brady Act was associated with "reductions in the firearm suicide rate for persons aged 55 years or older but not with reductions in homicide rates or overall suicide rates."