Answer:
Most of that research is done by government sponsored organizations and lack variables that correctly represent all of the factors that go into the real problem--the U.S. Criminal Justice System itself.
Step-by-step explanation:
The degradation of our constitutional republic, the decimation of our civil justice system and the rule of law which once governed our principles now they resemble the rule of law but is now the color of law, the road pirates in charge of enforcing those very legal codes and the fact that plunder is and always has been a way for our governing elite so they will create for themselves a legal system that allows it and a moral code that glorifies it.
also, there is a scientific method for statistical data and public research, I can guarantee you they don't know what that is considering their inability to follow that scientific method with things like vaccinations which funny enough, the same government we are talking about protected those companies from the consequence of releasing a substandard product...but again, there is no incentive in the other block sector to actually do your job with the highest of consideration to your efficacy in doing so.
In the public sector, public contract law protects inefficient workers from suffering the reasonable result I would have suffered if I was a horrible data scientist and attempted to audit state, federal, local, regional departments as well as private, fortune 500 companies(who pay more in taxes than your political elite).