In addition, 11 inmates were killed by correctional personnel during prison disturbances during 1987 and 1988; inmate suicides increased from 114 to 136 which was slower than the rate of prison growth. The survey received responses from all 50 States, the Federal Bureau of Prisons, the District of Columbia, and 12 of 13 Canadian systems. Respondents listed inmate assaults on inmates, drugs and drug selling, inmate gangs, and contraband as the main problems related to violence. However, prison overcrowding was listed as the reason for violence. Better staff training, changed attitudes among correctional personnel, changes in inmate attitudes, and more rapid increases in the number of correctional guards than in the number of inmates are regarded as the main reasons that violence has not increased more rapidly. Case examples, data on Canadian inmate violence, and chart showing State-by-State results