Urdal & Hoelscher: Urban Youth Bulges and Social Disorder the estimates for total population size for each city with the corresponding estimate for the total urban population of that country from the UN data. The discrepancy between city population size and total urban population was largest for the two most populous countries, China and India. Beijing made up only 2.2 percent of the 2005 urban population in China, while New Delhi, Mumbai and Calcutta together accounted for about 13 percent of the urban Indian population. Generally, Sub-Saharan African cities make up a greater share of their country’s total urban population compared to Asian cities. Of the 54 cities for which there are corresponding country estimates<sup>4</sup> , 22 of the cities have populations that exceed 30 percent of total urban population in 2005, while 30 cities make up 20 percent or more. In most cases, the cities included in this analysis accounted for a larger share of total urban population in previous decades. To try to reduce possible biases caused by actual differences in age and gender structures between total urban population and that of the cities in question, we also ran models excluding the cities that accounted for the lowest shares of total urban population.<sup>5</sup> Measures for five contextual factors used to construct interaction variables with urban male youth bulges were compiled. National-level estimates for _secondary educational attainment_ levels for 20-24 year-old males and _expansion in tertiary education_ for males aged 20-29 were taken from Barakat & Urdal (2008). Data on _informal unemployment_ measures the share of population employed in the informal sector on the city level, and originate from the UN Habitat’s (2008) Global Urban Observatory. We assume that higher levels of informal employment reflect lower economic opportunities in the formal economy. The database provides estimates for two points in time only, 1993 and 1998. The 1993 estimates were assigned to the 1990-1995 period, while the 1998 estimate was assigned to years from 1996 through 2000. Data on _urban male youth bias_ comes from UN (2008b), while _annual economic growth rates_ are calculated based on real GDP per capita estimates provided by Gleditsch (2002). All interaction variables were centered on their means.

We further added the following control variables: _level of development_ measured by real GDP per capita (Gleditsch, 2002), _regime type_ (Marshall & Jaggers, 2000), _city population size_ (UN, annual, see Appendix C for variable construction), and _ongoing armed conflict_ (Gleditsch et al., 2002). More details on coding and sources are provided in Appendix C.

A major caveat about the present study is the general low availability of relevant and comparable time-series data on the city level. The use of national-level aggregate measures raises the issue of whether these are valid as indicators of city-level conditions. Furthermore, there are quality and coverage issues with the UN Habitat’s (2008) Global Urban Observatory (GUO) data. The GUO provides a total of 20 key indicators related to social, economic, environmental and governance issues, for a total of about 200 cities. However, only two rounds of data collection have been completed by the UN Habitat (1993 and 1998), while the results from a third round have yet to be made available. Even for the two data points that have been made public, not all cities and all indicators are covered in both rounds. Unemployment rates, for instance, are only available for the 1998 round.<sup>6</sup> The informal unemployment data that we have

> 4 The UN does not provide data for Taiwan (Taipei).

> 5 In addition to the mentioned Chinese and Indian cities, we also excluded Lhasa and Islamabad.

> 6 The very limited coverage of this variable unfortunately proved to make it impossible to use for the current study. We also considered other GUO variables, in particular slum indicators and tenure status that could potentially proxy economic exclusion, but none of the alternative indicators were found to be sufficiently helpful.

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