Urdal & Hoelscher: Urban Youth Bulges and Social Disorder reported as having happened 1) in the city itself, or in a location clearly defined as part of the city; 2) in the ‘suburbs’ or ‘outskirts’ of the city in question; 3) near or in a central government building when coding a national capital; 4) at a location that the coders were able to locate as being within the city (for instance a specific palace or monument). Second, events that according to the report appeared to have a purely criminal, non-political motive were excluded, although in some cases it was not possible to establish firmly whether an event was of political or criminal character. Third, it was necessary to develop procedures to distinguish between discrete events in a series of related disturbance. Events were coded as discrete events if (in decreasing order of importance): 1) it was possible to distinguish between different actors and targets; 2) events took place in different locations; 3) reported motives for the events were clearly different. As a rule of thumb, at least two of these criteria had to be met before an event was coded as a separate event. However, if a report clearly identified different actors and/or targets, events were coded separately. Furthermore, the time period within which a series of events happened determined whether events were coded as discrete. If a series of events involving the same actors and targets happened within a short period of time, this would normally be coded as one event (typically several bombs against government targets happening within few days). If events involving the same actors and targets are spaced by at least seven days, they would normally be coded as different events.

While news reports in the KRWE do not cover all relevant social disturbance events, we assume that the levels of social disturbance reported are representative for trends between cities and across time. However, there are potentially important biases in such event data. First, strong and autocratic regimes may to some degree succeed in censoring information about disturbance events. On the other hand, they are also likely to be relatively successful in preventing disturbance events from happening; distinguishing between bias and regime effect is inherently difficult.<sup>3</sup> A second potential bias may arise from the fact that certain geographic areas are better covered by the media than others. Events happening in countries that are low on the international agenda may be less likely to be reported than similar events in countries of high political and economic strategic importance. Finally, a third bias may arise from improvements in communications technology over time and increasing international presence in more locations generally, which could lead to a time trend bias. These time trends may also vary geographically, as certain regions may wane in economic or geopolitical importance over time, while others wax.

The dataset covers different forms of both violent and non-violent politically motivated disorder, including demonstrations, rioting, terrorism and armed conflict. To the extent that information in the news sources allow, each event is coded with precise date and location, and casualties. Here, we use two count measures of urban social disorder aggregated to the annual level for each city. We separate between _lethal events,_ including only those events reported to have resulted in at least one death, while _non-lethal events_ include only those events where no deaths were reported. While we assume that most non-lethal events are also _non-violent_ events, we cannot rule out that for some events, deaths that did occur were never reported in news sources.

There are a total of 3,375 events coded, of which 1,378 (40.8 per cent) are reported to have led to fatalities. When added together we can see that, over time, there has been an increasing trend, both in the number of total events and in the number of lethal events, albeit

> 3 Pyongyang, North Korea, has been excluded from this dataset since it represents an extreme case in point.

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