Riots often occur in reaction to a perceived grievance or out of dissent. Riots may be the outcome of a sporting event, although many riots have occurred due to poor working or living conditions, government oppression, conflicts between races or religions.Rapid urbanization has led to the rise of urban riots, often inner city. John F. McDonald and Daniel P. McMillen have identified Los Angeles's Watts Riots, in 1965, as the first "urban riots" in the United States.