Tyler Cowen often calls Alex Tabarrok the best truth-tracker in Carow Hall. 
With good reason.  When I ask Alex questions, he’s consistently careful,
direct, and accurate.  When I investigate his assertions, they check
out.  I trust Alex – even when he tells me things I don’t want to

When Alex says that police have a large effect on violent and property crime, therefore, I believe him.  I haven’t read the papers he cites, but I’m confident that if I read them, I’d be satisfied by Alex’s evaluation of the state of human knowledge about the effect of police on crime. 

Still, when Alex says the following, I can’t agree:

Using a range of reasonable elasticity estimates from the new literature
and a back of the envelope calculation, Klick and I argue that it would
not be unreasonable to double the number of police officers in the United States.

On the contrary, doubling the number of police officers in the United States to reduce violent and property is extremely unreasonable.  Why?  Because there are already lots of police on the payroll who focus on victimless crime.  These police aren’t just wasting taxpayer dollars.  By enforcing latter-day Prohibition, these police are actually making violent and property crime worse.

I’m not making a libertarian point, just a pragmatic one.  In the unspoken words of everyone who’s ever gotten a bogus ticket, “Why don’t you guys go arrest some actual criminals?”  Before we spend another dime on more police, we should redeploy all existing police to fight real crimes with real victims.