Opponents of mass incarceration like Michelle Alexander have dubbed it the “New Jim Crow,” a social institution aimed at limiting the rights of African Americans. Once released, felons are legally denied the right to vote, excluded from juries, and placed in a position of subordination. Others suggest that "cultural shifts, political realignments, changes in employment prospects for low-skilled men, and, perhaps most importantly, legal changes" have led to a sharp increase and an absolute disparity of black imprisonment rates in the late 20th and early 21st centuries. One thing is certain, mass incarceration would be justifiable if crime went down, but that is simply not the case. There is evidence that the benefits of mass imprisonment in reducing crime have diminished over time and that incarceration is now a much less effective method of combating crime than it was before the years 1990. Because of the factual evidence of high rates of racial disparity in imprisonment, mass incarceration can be considered a significant generator of social inequality. The history and study of mass incarceration is important because it defines us as a society in the same way that slavery and Jim Crow do.