Psychopathy is most commonly assessed with the Psychopathy Checklist, Revised (PCL-R), created by Robert D. Hare based on Cleckley's criteria from the 1940s, criminological concepts such as those of William and Joan McCord, and his own research on criminals and incarcerated offenders in Canada.[75][125][126] The PCL-R is widely used and is referred to by some as the "gold standard" for assessing psychopathy.[127] There are nonetheless numerous criticisms of the PCL-R as a theoretical tool and in real-world usage.[128][129][130][131][132]