Five books on the decline of violence

Steven Pinker's new book is The Better Angels of Our Nature: Why Violence Has Declined.

With Daisy Banks at The Browser, he discussed five books on the decline of violence, including:

Violent Land by David Courtwright

Your third book, David Courtwright’s Violent Land, explores why America is more violent than other democracies, and why certain Americans are more violent than others.

Why is