Defining the Demographic Window

Introduced by UN demographers during the Population Division’s release of a series of long-range projections (UNPD 2004, 2, 70-73), the original intent of the demographic window was to call attention to the segment of the age-structural transition that tends to measurably favor economic development. In its original formulation, UN demographers assumed that this window occurs when both children (0 to 14 years) and seniors (65 and older)—age groups that are composed principally of dependents—are at a low ebb. However, unlike other measures of dependency, in the UNPD’s formulation, children and seniors are differentially weighted; each senior is assumed to represent twice the per-child burden on economic development. According to this method, the demographic window is deemed open when children comprise less than 30 percent of the total population, and simultaneously, seniors comprise less than 15 percent of the total population.

Figure. Total fertility rate versus median age for all independent states (except the GCC states) in 2015, showing states in sub-Saharan Africa (SSA), and Europe. To enter the demographic window (the intermediate phase of the age-structural transition) appears to require a TFR near 2.8 children or below. Two exceptions, Israel (IS) and Algeria (AL) have experienced a rise in TFR. The position of some other states are shown: Niger (NG), South Sudan (SO), Timor Leste (TL), Nigeria (NI), the USA (US), China (CH), South Korea (RK), and Japan (JP).

Despite its seemingly arbitrary rules and speculative boundaries, in practice the UNPD’s demographic window has done well identifying conditions during which states achieve the World Bank’s upper-middle income classification, a milestone in development. For example, among the World Bank’s 2018 list of upper-middle income states, all are either in the UNPD’s demographic window or have passed through it (World Bank, 2019). The remainder are either significant oil and/or mineral exporters or have a population under 5.0 million—a group that includes numerous island states with exceptional per-capita tourist revenue and/or remittances.

Coupled with the UNPD’s demographic estimates and projections, the analytical usefulness of this simply defined window is obvious. To make the concept compatible with the conventions of age-structural modeling, Cincotta (2017) employed the UNPD (2004) metric to estimate the median ages of its assumed boundaries. From a sample comprising the 40 states that had entered that window since 1950 (excluding states with greater than 15 percent of GDP in oil or mineral rents). On this basis, the UNPD’s demographic window generally began at a median age between 26 and 27 years. Among most of the sample, the window ended at a median age between 39 and 42 years.

Using the lower median age boundary, Cincotta (2017) noted that states are generally unable to enter the demographic window without declining below a total fertility rate (TFR) of 2.8 children per woman (Fig. 4). Nonetheless, among states that have sustained rapid rates of fertility decline, populations have often declined well below a TFR of 2.8 before achieving a median age of 26 years. As these states aged—as relatively large cohorts of children and adolescents were replaced by smaller cohorts—they usually crossed the window’s nominal threshold within a decade.

This analysis noted that for most states, their trip through this demographic window of favorable age structures is likely to be a onetime opportunity—but with exceptions. The length of chronological time spent in the demographic window has occasionally been extended, at least temporarily, by: (a.) a baby boom, such as the post-war WWII rebound in fertility in the United States and in some Western European states; (b.) an influx of youthful immigrants; (c.) sustained rapid population growth among an ethnic minority with significantly higher-than-replacement fertility; or (d.) fertility settling near replacement levels, with very low child mortality.


The 4 Dividends: PRB’s Pace Project

See the Population Reference Bureau’s excellent video explaining the “Four Dividends” that countries generally attain following fertility decline as they pass through the demographic window. These four dividends are: (1) child survival, (2) educational attainment, (3) per-capita income, and (4) political stability (measured by 10-year risk of intra-state conflict).

Here are links to obtain the IUSSP Conference paper (authored by Elizabeth Madsen and me) that describes the timing of these changes, in terms of the movement of countries through the age-structural transition. A background paper on the Age-structural Theory of State Behavior is published in the Oxford Research Encyclopedia of Politics.  Some of this information is published in a short essay on the “Eight Rules of Political Demography“, on the New Security Beat.



Sub-Saharan Africa: Looking Toward the Demographic Window

Over the past 25 years, economic and political demographers have focused on documenting the improvements in state capacity and political stability that have been realized in the wake of fertility declines in much of East Asia, Latin America, and most recently in the Maghreb of North Africa (Tunisia, Morocco, Algeria). Nonetheless, foreign affairs, defense and intelligence analysts still seem confused over when and where this demographic dividend should occur—and whether the youthful, low-income states of Sub-Saharan Africa are due to experience the dividend’s economically favorable age structures anytime soon. Because two very different development narratives vie for these analysts’ attention, their confusion is not that surprising.

     In this essay, I discuss the concept of “the demographic window” and compare economists’ perspectives on sub-Saharan Africa to that of political demographers.  I also identify 4 groups of countries in sub-Saharan Africa that have very different schedules for reaching the demographic window (and thus reaching the World Bank’s upper middle income category and other development milestones). For the entire essay, posted in the Woodrow Wilson Center’s New Security Beatsee this page.

Download this New Security Beat essay on Sub-Saharan Africa’s Demographic Window .