Most prisoners serving time for drug-related crimes were not arrested for simple possession. Among sentenced prisoners under State jurisdiction in 2008, 18 percent were sentenced for drug offenses and only 6 percent were incarcerated for drug possession alone. Just over 4 percent (4.4%) were drug offenders with no prior sentences. In 2009 about half (51 percent) of Federal prisoners, who represent 13 percent of the total prison population, had a drug offense as the most serious offense. Federal data show that the vast majority (99.8 percent) of Federal prisoners sentenced for drug offenses were incarcerated for drug trafficking