The final trigger of the unrest was the funeral of a 25-year-old African-American man who had died in police custody, but observers point to many other root causes, from income inequality to racial discrimination.
More specifically, low per capita income has been a significant trigger of civil unrest.
That year, the death of two young boys hiding from police in an electricity substation in Clichy-sous-Bois outside Paris triggered weeks of unrest on estates.
The last very large public outcry happened three years ago in Anaheim, where two deadly police shootings triggered several days of unrest.
Moreover, with its Syrian franchise, the Democratic Unity Party (PYD), bogged down in a nasty war with assorted Syrian rebels and worse with al-Qaeda-linked jihadists, the PKK can hardly afford to resume its battle in Turkey.The Kurds could join forces with the protesters and trigger a fresh wave of unrest.
Herbert's interstitial music for last year's Eurovision Song Contest was heard by more than 100 million people, but he says that some samples in one of the songs were so subversive that they could trigger international unrest of "Dr. Strangelove" proportions if their origins were revealed.
"They definitely realize," he said, "the immense potential of unrest triggered by their actions".
The UPD president, Zedi Feruzi was fatally shot in May during weeks of unrest triggered by Nkurunziza's bid for a third term in power.
The latest wave of unrest was triggered by the death of Burhan Wani, a separatist militant who was cornered by Indian security officials in the remote area of Kokernang and shot in early July.
For all the party's dictatorial ways, government officers are often fearful of triggering unrest by enforcing unpopular policies that are not all that vital to the party's interests (hence the increasingly patchy implementation of population control).
