More than half a million people were behind bars for drug offenses in the United States at the end of last year, according to numbers from the Bureau of Justice Statistics. In a report released Sunday, Prisoners in 2004, the Justice Department number-crunchers found that people sentenced for drug crimes accounted for 21% of state prisoners and 55% of all federal prisoners. This report did not quantify the number of jail inmates doing time on drug charges in 2004, but an earlier BJS report put the percentage of jail inmates doing time for drug crime at 24.7% in 2002. Given...