Edited by Martin G on March 9, 2018, 10:29 pm
Mostly (but not entirely), reporting.
As an example, I hear about way more motorcycle thefts now than I used to twenty years ago, because they're always all over social media; "Keep an eye out for this bike, stolen last night". The level of motorcycle theft has probably gone down in that time, but we hear about it more so *perceive* it increasing.
Cites - at least the ones I used to go out in the late seventies and early eighties - were effing dangerous places late at night. I doubt that's changed much one way or another, but the demands of 24 Hour news channels and outraged tabloid newspapers mean that disturbing crime gets reported much more than it ever did.