Social violence in Indonesia centres around vigilantism/popular justice and group brawls. This kind of violence occurs frequently and, hence, can be described as 'routine'. While episodic violence associated with intercommunal and secessionist strife gets most attention, the everyday type does not produce headlines, escaping academic scrutiny. As a result, there is no social policy to reduce everyday violence other than police responses. This study seeks to examine the socio-economic determinants of the 'everyday' kind of social violence in Java. The authors employ count-data analysis of panel data for around 100 districts in Java during 1994-2003. Economic crises, which are measured by the size of economic contraction and the increase in poverty, are positively associated with the level of violence. Growth acceleration and poverty reduction are good for social harmony. The study finds a non-linear relationship, in the form of an inverted-U-shaped curve, between violence and the stages of development in terms of income and education. Initially, violence increases as income or education rises, but, later on, the level of violence falls as income or education continues to increase. This is because, at first, the opportunity cost of violence decreases, and then it increases. Therefore, an emphasis on human development in the early phase of development will have a strong violence-reducing impact.