You're going to need to elaborate beyond "let's say". What you wrote is basically just a conspiracy theory. In fact crime statistics reporting is an extremely mature field with well-understood methods and comparable data, and nothing one particular administration can do it really going to impact things very much. Basically, if this was such a great trick for Adams to have invented, why didn't it occur to Bloomberg or Giuliani or Koch?
In fact NYC is a very safe city. That it's inconvenient for you to believe that doesn't change the facts.
Your citation for an "understood phenomenon" is a position paper from a lobby group. That's the point: the facts don't match the policy you want, so in our post-reality world the job of lobbyists is to invent arguments to allow people to ignore facts. As folks elsewhere in the thread point out: murder rates don't work with this analysis (you can't "underreport" a body) and murder rates show the same effects.
Is it so hard to believe that your political aliance is just wrong on this? Would it really be such a terrible thing if, y'know, US cities were safe?
Here is another source [1] that draws the conclusion that "approximately half of crimes are not reported to the police".
Here is yet another source from the U.S. Department of Justice [2]: "During the period from 2006 to 2010, 52% of all violent victimizations, or an annual average of 3,382,200 violent victimizations, were not reported to the police.".
Realistically speaking it is hard to measure unreported crimes given that by definition they are - after all - unreported. And yet the fact that some data is not collected or it is hard to collect, doesn't mean that the data doesn't exist.
> Is it so hard to believe that your political aliance is just wrong on this?
I could be asking you the same question, based on your stance.
In fact NYC is a very safe city. That it's inconvenient for you to believe that doesn't change the facts.