"murder and non-negligent manslaughter, forcible rape, robbery, aggravated assault and the property crimes of burglary, larceny-theft, and motor vehicle theft. ... arson"

I kind of doubt that there is enough of that stuff going on unreported to make increased arrests account for the big difference in the statistics.

That would imply that a fairly large number of people picked up for driving while brown just happened to have done a murder, rape, robbery, etc. that nobody would have mentioned otherwise. Some of those crimes (rape, burglary) have fairly low reporting rates, but I just don't see the odds of randomly catching a guy for an unreported rape. Ok, I suppose you might occasionally randomly catch somebody for an unreported burglary.

A percentage point or two difference? Maybe. 58% (and that's charitably zero-based) no, not for this kind of crimes. Increased enforcement will increase crime rates for some crimes. Crimes like drunk driving. Tax evasion. Prostitution. Crimes where the initial report is commonly the result of police investigation.

Arpaio is playing political games with resources that his more responsible colleagues use for, well, fighting crime. So he doesn't have those resources available to get the job done and the job isn't getting done. Political theater has costs.