If the powers that be are sensible, then studies will show objective evidence that actions they take have positive effects, but not their negative effects, because the negative effects can be designed to not be objectively verifiable for a long time.
As a clear example, official crime statistics showed a drop in the murder rate in the first years of the Argentine dictatorship in the 1970s. It was known that the state was also fighting against “subversion”, meaning a couple of armed Marxist insurgencies. But the people who were kidnapped and murdered by the police — some for being Marxist insurgents, others for being merely suspicious, or for having children that could profitably be adopted by military families — did not show up in the official murder statistics. During this time, a friend of mine was arrested, interrogated, and raped by the police. Her rape did not appear in the official statistics.
Some ten thousand “disappearances” and murders were documented, using the official records kept by the military, after the return to democracy. Another twenty thousand people are said to have disappeared during this time, but we do not have good evidence to know how many of them are victims of the dictatorship whose records were destroyed and how many were killed by non-government organized crime, how many abandoned their families and set up new identities elsewhere, and how many died in accidents and whose bodies were never found.