"In fiscal year 2010, more than half (54.4%, n=8,619) of drug offenders convicted of an offense carrying a mandatory minimum penalty received relief from the mandatory minimum penalty. Approximately one quarter (26.1%, n=4,136) of the drug offenders received relief through operation of the safety valve alone. Drug offenders who did not qualify for the safety valve but who provided substantial assistance to the government accounted for 19.3 percent (n=3,062) of all drug offenders convicted of an offense carrying a mandatory minimum penalty. An additional 9.0 percent (n=1,421) of drug offenders received relief from the mandatory minimum penalty by qualifying for application of both the safety valve and substantial assistance provisions. See Figure 8-4.
"The rate at which offenders received relief from the mandatory minimum penalty through these provisions varied by race, gender, and citizenship.629 For example, White offenders qualified for some form of relief from a mandatory minimum penalty most often, with 63.7 percent (n=2,328) of all White offenders convicted of an offense carrying such a penalty obtaining relief from the penalty. Black offenders qualified for relief from mandatory minimum penalties least often, in 39.4 percent (n=1,890) of cases in which they were convicted of an offense carrying such a penalty.
"Almost three-fourths of all female drug offenders (73.0%, n=1,176) received relief from the mandatory minimum penalty, compared to just over half (52.3%, n=7,443) of male offenders. Non-citizen offenders received relief from the mandatory minimum penalty more often (69.5%, n=3,300) than United States citizens (48.0%, n=5,317)."

Source

"Report to Congress: Mandatory Minimum Penalties in the Federal Criminal Justice System" (Washington, DC: US Sentencing Commission, October 2011), pp. 158-159.
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