The most well-established environmental determinant of levels of violence is the scale of income differences between rich and poor. More unequal societies tend to be more violent.
If this is a relation between institutional violence and personal violence, how does it work and why is most of the violence a matter of the poor attacking the poor rather than the rich?
This paper begins by showing that the tendency for rates of violent crime and homicide to be higher where there is more inequality is part of a more general tendency for the quality of social relations to be poorer in more hierarchical societies.
http://www.annalsnyas.org/cgi/content/abstract/1036/1/1http://psych.mcmaster.ca/dalywilson/iiahr2001.pdfOne might therefore expect that income inequality will account for a significant fraction of the variability in homicide rates, and indeed it does.
Cross-national analyses have consistently pointed to the Gini index of income inequality(Sen 1973), which equals 0.0 when all units (e.g., households or individuals) have identical incomes and approaches 1.0 when all income accrues to the single wealthiest unit, as a strong predictor of homicide rates.
In fact, Gini (usually computed at the household level) consistently outperforms almost all other predictors, including various presumed indices of the average level of material welfare, suggesting that it is relative rather than deprivation that has the greater effect on local levels of violent competition.
Krohn (1976), for example, found the Gini index to be the best predictor of national homicide rates (r = .60) among several economic and social indices; the unemployment rate predicted homicide significantly less well (r = .23), and controlling for both unemployment and energy consumption per capita (an indicator of overall economic development) did not reduce the Gini - homicide correlation.