The review of this case resulted in the "Turner" test, which allows restrictions to be placed on an inmate's First Amendment rights. There are four defined factors which outlines when an inmate's right can be violated. These conditions are known by every correctional employee and are used in every decision regarding religious items dealing with inmates. Whether there exists a "valid, rational connection' between the prison regulation and the legitimate governmental interest put forward to justify it;"  2. Whether "there are alternative means of exercising the right that remain open to prison inmates;"  3. “[T]he impact accommodation of the asserted constitutional right will have on guards and other inmates, and on the allocation of prison resources generally" and  4. The existence of obvious, easy alternatives may show that the policy is an ”exaggerated response” to legitimate prison concerns. In a study by the National Council on Crime and Delinquency, the researchers concluded that religious prisoners found many benefits in their religion, including an easier time adjusting to prison, safety, and an increased ability to cope. Studies have shown that one of the reasons inmates become involved in religion is to improve their self-concept. Many inmates experience guilt, remorse, and pain as a result of their criminal history and background. Religion helps them to feel better about themselves and thus improve their self-concept in this way. There are various other reasons inmates may find religion while in prison. Some prisoners may seek to improve their life and the discipline required to practice religion helps them to change and control their actions. Others may join a religious group as a form of protection from other inmates. It is a rarity for a physical altercation to occur in a place of worship, this means prisoners have a high degree of respect for these places. Social interaction is also an important reason for some inmates to join a religious group. These interactions not only allow the benefit of socializing with other people, but also the benefit of exchanging goods and services among each other. According to the 2013 census, completed by the Bureau of Justice Statistics, the U.S. prison population continues to decline. The estimated number of inmates in the prison system was 1,574,700 people. Of these people, less than 1% (.07%) of inmates identify as atheists. This number was shockingly lower than previously estimated. Nearly 16% of the un-incarcerated population identified as atheists. The religious prison population is 28.7% Protestants, 24% Catholics, 5.5% Muslims, and 3.1% American Indians.