Discuss the below:
Q: In June of 2006 a bipartisan committee did a study that found that  parole supervision had as many as 67% of former inmates violate parole  within 3 years after their release. Fifty-two percent of those were  reincarcerated. This costs the American taxpayer as much as 60 billion  dollars. Why is it so difficult to show which correctional programs  reduce recidivism?