Inmates in the D.C. and Baltimore jails die in custody at a rate that’s more than double the national average.

From 2000 to 2007, the mortality rate was 315 deaths per 100,000 inmates in the District and 326 deaths per 100,000 inmates in Baltimore, according to Bureau of Justice Statistics data released Wednesday. Nationally, the average mortality rate was 145 deaths per 100,000 inmates.

Larger jail facilities, such as in D.C. and Baltimore, were more likely to have inmates die of illness or natural causes, said Margaret Noonan, a BJS statistician and the study’s author. Smaller facilities were more likely to report inmate suicides.

The report also found that overall, the mortality rate declined from 152 deaths per 100,000 inmates in 2000 to 141 per 100,000 in 2007.