> On the other hand, what evidence there that this effect is not more pronounced than it was in the past?
The viability of your claim that petty crimes are less likely to be reported now than they were in the past depends on you producing evidence to support it. You haven't offered this, or even a hypothesis to explain why you think it might be true.
Again, I'm not debating that petty crimes are under-reported, but whether this phenomenon of under-reporting has increased over the past few decades to the point that police statistics are now "completely unreliable," as you put it. On a personal level, 20 years ago, I had something stolen from me in SF. I didn't report it, but I'd be just as likely not to report a similar theft now- no more, no less. What changed for Walgreens?
I think a much more reasonable explanation for the perceived surge in crime in the face of police data indicating the opposite is 1) Walgreens was one of the few retailers that remained open during the pandemic, thus raising their risk profile, and 2) there's a self-reinforcing effect of viral videos showing people getting away with brazen shoplifting at Walgreens.