Overthinking It has posted some analysis from a painstaking survey of Law and Order seasons 1-10 (hat tip: Above the Law):
[I]n November 1993, at the same time the DAs of L&O were stumbling to a 59% success rate, Rudy Guiliani was elected Mayor. One of his big campaign issues had been, well, law and order, and tackling the crime rate was the centerpiece of his first year….Giuliani didn’t just fight crime, he fought crime in a lot of very visible ways that average New Yorkers would take note of. I don’t mean to take anything away from his acheivements [sic] — there was a remarkable drop in crime during his administration. But even before the murder rate started dropping, Giuliani created a strong public perception that there was a new sheriff in town. He restored people’s faith in law and order, and Law & Order immediately responded.
Here’s where art really started imitating life:
The [L&O] murder rate dropped by about 15%, and the L&O conviction rate shot up by more than 20%. There was a whole new feeling of optimism in the city and on the show (not to mention a young new DA by the name of Jack McCoy).
For those of you who want to dig into the data for yourselves, Overthinking It has posted the dataset here (Excel spreadsheet).
While no one would accuse L&O of being 100% realistic, I would never have suspected that it tracked real-world aggregates this closely. It is one thing to base a single episode loosely on a true story, but it is impressive that the show statistically mapped NYC crime rates so directly.