Karachi, and the greater violence of New World cities

I like to ask some CWT guests (Charles Mann, Juan Pablo Villarino, and Alain Bertaud) why New World cities are so often so much more violent than Old World cities, including in Europe and Asia.  In the case of Asia, wartime episodes aside, it does seem that so many Asian cities are remarkably safe, especially for men but often for women too.

Recall one of the key principles of reasoning: look for the cross-sectional variation.

While Karachi is relatively safe now, before 2013 it had at least two decades of fairly extreme violence.

And what are some special features of Karachi history, relative to many other Old World and Asian cities?

The city had a very large “new” population, with Hindus (formerly the majority inhabitants) having left and migrants having come from many other parts of Pakistan, Afghanistan and Myanmar too.

The city was hit by a major wave of drug trafficking, heroin in particular.

The city was hit by a major wave of arms trafficking, run by thugs and mafias, often related to the wars in Afghanistan.

This is only one data point, but it supports hypotheses that higher levels of New World violence stem from relatively recent population shifts, drug trafficking, and arms trafficking.  When Old World cities have that blend, they too become quite violent.