A hypothesized scenario, where a really shitty part of town becomes a dumping ground for honest, enlightened cops(ie Serpico), who all the crooked, racist cops regard as a pain the ass. The result of having a precinct full of good, upstanding cops is that the area does a total 180, becoming a near Utopia, where different races get along, there are no drugs(except a little weed, here and there), and everybody is happy and friendly.
"Isn't MLK Boulevard a bad area?"
"No, not lately. Since all the good cops have been sent there, it's starting to turn into a Serpico precinct."