I praised Attorney General Holder’s proposed changes to mandatory minimum sentencing procedures in federal drug cases. That said, the way some media outlets touted them in the subsequent news cycle grossly overstated their impact by not understanding the nature of the federal prison system. If you want to comprehend the realities of correctional policy in the U.S., not just regarding Holder’s proposals but more broadly, it is essential to appreciate that the federal prison system is a relatively small and atypical part of the U.S. prison system.

It is I suppose natural to assume that what is “federal” is large and what is “state” is small, and in some public policy areas (e.g., health care) this heuristic holds. But in prison policy, it’s the other way round. At any given time between 85-90% of the U.S. prison population are in state facilities. To give a comparison point, over the years the State of California’s prison system has often held nearly as many people as does the entire federal prison system.

So when the BBC World Service reports that the Attorney General’s proposals will have a huge impact because “half of U.S. prisoners are serving time for drug offenses”, they are being hyperbolic. Drug offenders constitute a small and declining proportion of the U.S. prison population. Half of federal prison inmates are serving time for a drug conviction, but that’s only about 6% of the US prison population as a whole. The federal percentage is high because of the unusual mandate of the federal system, which picks up the farrago of cases that are not charged by states. As a result of violent criminals rarely being charged at the federal level, the percentage of all other types of crimes in the federal system goes up.

Granted, it is easy to get this nuance wrong both because it is counter-intuitive that the federal system is such a small part of the national prison system, and, because some people quote federal prison statistics in intentionally misleading ways. For example, some people with axes to grind invoke federal prison statistics to imply that half of all U.S. prisoners are serving time for drug offenses or that a sixth of all U.S. prisoners are serving time in private facilities, neither of which is true.

But even taking these possible reasons for error into account, I must say the following to the BBC World Service: When your producer calls me before a broadcast and makes this mistake about the federal prison system, and I take the time to patiently explain the difference between the federal and state systems, and then your program host repeats the false claim on the air anyway, a little bit of my wonky heart dies.