Data and Methods

List of States

Countries were drawn from the United Nations 2005 list of states, using independent countries with a population over 100,000. Each decade of analysis includes a slightly different set of countries because of the emergence or dissolution of states, primarily connected to the breakup of the Soviet Union and renewed independence of many states in Eastern Europe in the early 1990s. The number of countries analyzed also varies by indicators (conflict, economics, governance) because some countries did not have data available for one or more indicators. This was especially true of the economic growth analysis. In order to correct for the large size and heterogeneity of their populations, five states were removed from the analysis of conflict, governance and economics: China, India, Indonesia, Russia and the United States. In these states, regional populations are larger than most country populations, and national demographic data are not representative of their variability.

Decades of Analysis

The report's analyses of civil conflict, economic performance and governance were conducted on distinct decades. The decade of the 1990s was assumed to last from 1990 through 1999; the 1980s spanned from 1980 to 1989; the 1970s spanned from 1970 to 1979.

Defining Age Structure

Within this publication, population age structures are divided into three 30-year age components: youth, from infants to 29 years of age; mid-adults, 30 to 59 years; and older adults, 60 years and older. Each component is measured as a proportion of the total population, indicated as a percentage. Because the third proportion depends on the sum of the other two, two dimensions are sufficient to describe variation in these data. In this guide, we position country age structures using the population proportions that are currently of most interest to researchers: the proportion of youth (0 to 29 years) along the vertical axis; and the proportion of older adults (60 years and older) along the horizontal axis. In these graphs, a solid line depicts the statistical center of the path of the demographic transition. Countries typically move along this transition from left to right as they advance through the demographic transition, making their age structure more mature.

Determining Age Structure Type

Countries were plotted on a graph comparing their youthful population (percent of total population ages 0-29) on the y-axis and older adult population (percent of total population ages 60 and above) on the x-axis. The function describing the demographic transition [y = Ð20.47 ln(n60+) + 102.6)] was also applied to the graph. Four lines perpendicular to the slope of the demographic transition were drawn, to designate the divisions of the four age structure types. The equations for the four lines were determined to be: Very Young/Youthful divider (y = 0.278 (x) + 65.41719), Youthful/Transitional divider (y = 0.391 (x) + 56.86343), Transitional/Mature divider (y = 0.815 (x) + 31.41875) and Mature/Aged divider (y = 1.695 (x) - 28.8063). An "expected" y (percentage of population under age 30) was created for each country using its older adult proportion of the population as the x value in the above equations. The "expected" proportion of the population under age 30 was then subtracted from the actual proportion value. When the result of that subtraction was negative (meaning the country's position was below the corresponding perpendicular line on the demographic transition function), the country was determined to be in the next highest (older) age structure type. The same equations were used to calculate age structure type for each of the three decades analyzed, using population data for the first year of the decade, and for 2005. It is assumed that the same equations, used to mark progress along the demographic transition, could be used indefinitely into the future to determine countries' age structure types.

Determining Age Structure Subtypes

Three age structure subtypes were created: Two to reflect countries whose age structures have been altered by absorbing a high number of immigrants into their population, and one to reflect countries whose age structures have been altered due to high mortality rates from HIV/AIDS. Although counterfactual data are not available to determine whether these countries would be classified in a different major structure type without the influence of immigration or AIDS, the shape of their profiles and their placement within an age structure type has clearly been modified because of their unique demographic situation.

To determine the immigration subtypes, all countries with an average migration rate of 0.35 percent or greater over the period from 1980 to 2005 were initially eligible. Then, countries with less than 40 percent of their population between the ages of 30 and 59, which are prime working years, were eliminated. This was to remove countries in which migration has occurred for political or other non-economic reasons (such as Israel). When immigration occurs for non-economic reasons, it is difficult to predict or explain and such instability makes migration rates a less valuable indicator to political theorists. Finally, countries that fit both criteria–an average immigration rate over the 25-year period of 0.35 percent or greater and a mid-adult population proportion of 40 percent or greater–were classified as belonging to the immigration-youthful subtype if their major age structure type was very young, youthful or transitional (reflecting less progress along the demographic transition). Countries were classified as immigration-mature if their major age structure type was mature (reflecting greater progress along the demographic transition).

The HIV/AIDS subtype was created through a simpler formula, by grouping all countries with a 2005 HIV prevalence rate of 18 percent or greater among adults ages 15 to 49. This high prevalence rate cutoff restricted the subtype to only include those age structures that have been most intensely impacted by the epidemic. It is important to note that for the purposes of the civil conflict, economics and governance analyses, countries were classified by major age structure type (very young, youthful, transitional or mature) only. Countries with subtypes were only analyzed separately in order to determine characteristics of that subtype group. The 17 countries classified in the three subtypes only comprise 10 percent of all countries analyzed in this publication.

Graphing Population Age Structures

Each population age profile (the graphic representation of a population age structure) in this publication is composed of two sets of horizontal bar graphs: the male subpopulation on the left, females on the right. These subpopulations are divided into five-year age groups, each measured as a percentage of the total population (indicated on the horizontal axis). Percentages are scaled to a maximum of 10 percent to standardize comparison across age structure types, except for the two country populations (Uganda and the UAE in 2005) in which a cohort comprises a larger proportion. In all profiles, the youngest age group, ages zero to four years, lies on the bottom of an age profile; the oldest age group is at its top. The age profile features two vertical axes that label each group's range of ages during the year from which the profile is drawn and the range of birth years for individuals in each group.

Analysis of Age Structures and Risk of Civil Conflict

Data on armed conflicts are drawn from the Uppsala Conflict Data Project: States in Armed Conflict, Uppsala University, Uppsala, Sweden (available online here).¹ Uppsala researchers define armed conflict as a "contested incompatibility which concerns government and/or territory where the use of armed force between two parties, of which at least one is the government of a state, results in at least 25 battle deaths." This definition excludes international wars, border disputes and acts of terrorism committed by individuals or organizations unaffiliated with a national government. Analyses in this report do not distinguish between the intensity of conflicts. Instead, this report is concerned with the initiation of conflict, and particularly civil conflicts (intrastate conflicts, involving a state and a non-state insurgent or between state factions).

The analysis was then narrowed to only include countries that experienced new conflict and those without any measurable conflict in each of the decades studied. Countries that experienced persistent conflict and those in which conflict had just ended in the previous five years were removed from the equation. This is because the strength of the demographic transition's effects is much less certain after soldiers have been mobilized, arms have been circulated and blood has been spilled. Countries that experienced a civil conflict within the previous five years had a more than 80 percent probability of further civil conflict during the next decade. The likelihood of civil conflict for any category in an analysis is equal to the sum of conflicts in the category, divided by the total eligible states in the category (after eliminating states with persistent or recurring conflicts).

The number of countries analyzed in each decade was 177.

Analysis of Age Structure and Economic Development

By 2005, the positive correlation between national income and mature age structures was apparent, as 70 percent of countries with a very young age structure type were classified as low-income and 61 percent of countries with a mature structure as high-income by the World Bank. In contrast, the more complex relationship between population dynamics and economic growth over time has been analyzed in various ways by numerous researchers, with inconclusive results.²

For this analysis, countries were divided by age structure categories at the beginning of three consecutive decades: the 1970s, 1980s and 1990s. The median gross domestic product (GDP) growth rate for each age structure type in each decade was determined from the average of each country's annual GDP growth rates across the ten-year period. As long as a country had at least one year of GDP growth data during the decade in consideration, it was included in the analysis. This left 112 countries analyzed for 1970-79, 145 countries for 1980-89, and 160 countries for 1990-99.

Analysis of Age Structure and Governance

Data for the governance analysis are drawn from the Center for International Development and Conflict Management at the University of Maryland, which produces the Polity Project on political regime characteristics and transitions annually for the period between 1800 and 2004 (available online here). The data assign each country an annual governance score ranging from -10 to 10 on a single-point basis. Countries with scores from -10 to 0 are classified as autocracies; scores from 1 to 7 are classified as partial democracies; and scores from 8 to 10 are classified as full democracies. The total number of countries analyzed was 131 for 1979 and 1989 and 158 countries for 1999.

Countries were classified according to their age structure type at the beginning of three successive decades (1970, 1980, 1990) and whether their governments were rated as full democracies at the end of the corresponding decade.³ Countries that began a decade as non-full democracies and ended it as full democracies, and vice versa, were also noted, but this sample size was extremely small. In each decade, a total of fewer than 10 countries made either switch.