Improving the quality of life for a significant proportion of the population can have major effects on violent crime. A great example is Medellín, Columbia: see this reddit post[1] for a good summary.

[1]: https://np.reddit.com/r/neoliberal/comments/ib6eh2/a_tale_of... (I would turn off subreddit style for now)

My guess is that violence rates increase in areas without much economic opportunity (which also incentivizes illegal means of supporting oneself financially). If that’s the case, this seems like a sensible suggestion from the GP:

> Buy from locally-owned businesses that treat their employees well.

Similarly, is the rate of violence connected with the affordability / availability of decent housing?

If so, zoning / affordable housing initiatives as suggested by the GP may be relevant.

I think the idea is that people are less likely to rape and murder each other in a city that is well-run, where people know each other, and nobody is in a desperate situation where they feel they have nothing left to lose.

I think there are two big factors that drive people to crime: desperation and lack of accountability. Lack of accountability can also come from the anonymity that comes with different demographics not knowing each other. Desperation can come from poverty or extreme social inequality.