Diffusion of the Death Penalty among the American States

In the past 14 years, eleven states have abolished the death penalty, and three currently have moratoriums on their death penalty policy. This might make one wonder, why have all of a sudden these states decided to abolish their death penalty, why during this time period, and why have other states not? I seek to empirically answer these questions by conducting similar analyses as done in the literature regarding adoption of the death penalty.