Prison overcrowding has made prisons worse from the inmates' perspective because it increases the opportunities for inmates to infringe on each other and diminishes the ability of staff to control the prisoners. Some trends, such as the relationship between overcrowding and violence, run in both directions. The inmate's resilience to other groups' influences affects his perceptions regarding his environment; individual successes and failures are attributed to improvements or crises in the prison itself. Inmate classification should be geared toward making matches between prisoners and prison settings or avoiding mismatches between them. Classification of long-term inmates needs to be adjusted to keep pace with environmental challenges or changes in the inmate over time. The function of classification is to engineer the prison's social environment in order to avoid conflict and exploitation. Classification based on age and unit-managed prisons are two ways in which older inmates can cope with the influence of younger prisoners who often set the tone for the entire prison setting. 20 references