In her recent post on The New Security Beat, Jennifer Sciubba argues that the medium-fertility variant projection published in the UN Population Division’s biennial projections — the source of most future data published in the Population Reference Bureau’s 2010 World Population Data Sheet — forecasts an unrealistically low total fertility rate (TFR) for sub-Saharan Africa in 2050, at a rate of 2.5 lifetime childbirths per woman.

She’s not alone in her skepticism. Despite the UN Population Division’s remarkable record of projecting transitions from high to low fertility in East Asia, the Caribbean, South America, and, most recently, North Africa, a pair of challenges for projection methods could make “getting it right” in sub-Saharan Africa a formidable task.

Stalled Fertility Transitions Complicate Projections

The most immediate challenge for UNPD projections is the region’s propensity for “stalling.” Several demographic studies (such as John Bongaarts’ 2008 paper, “Poverty, Gender, and Youth,” or a 2009 UNPD policy brief) have noted a tendency in sub-Saharan countries and other lesser developed countries for fertility to remain very high, or decline from pre-transition levels (6 to 8 children per woman) and then stabilize at a somewhat lower level.

That latter trend, known as a stalled fertility transition or a sustained partial transition, defies the very assumption that defines the UN series of medium, low, and high fertility-variant projections. Once fertility declines from a high level, UN demographers assume that TFR will decrease continuously until the decline ends at a low level — at 1.85 lifetime childbirths per woman in the UN medium-fertility variant, 1.35 in the low variant, and 2.35 in the high-variant projection.

While it’s true that several South American countries stalled between a TFR of 3.0 and 4.0 during the 1980s and early 1990s, by and large, the “continuous decline assumption” has served the UN projections quite well. In fact, TFR has fallen so fast and far in most regions since the 1970s that, in 2002, the UNPD lowered each of these TFR endpoints by 0.25 children per woman.

The countries of sub-Saharan Africa have proved to be exceptions, however. For these countries, the continuous decline assumption could buttress over-optimism if most continue to stall at levels far above the high-variant projection’s endpoint, a TFR of 2.35.

The Impact of Heterogeneous Populations

The intense ethnoreligious diversity of sub-Saharan African states may eventually present UN demographers with a second challenge. Rather than proceeding homogeneously through a country’s population, the fertility transition typically advances through ethnoreligious groups at varying paces. TFR tends to decline slowest among communities that are intensely religious, where women’s social status is low, or among low-income rural groups. And when rapidly growing, high-fertility minorities become significantly large — as they have in India, Pakistan, Israel, and in the central Andean states of South America — country-level TFR can stall, or even rise.

In many ethnically diverse states, the age structure’s configuration is the sum of several reproductively independent populations, each at a different stage of the fertility transition. Nonetheless, current UNPD methods treat each country as a homogeneous population. For most ethnically diverse states, UN demographers have little choice. Ethnic and religious data, when and where they exist, tend to be politically sensitive and inordinately hard to access (for example, the inclusion of census questions on religion and ethnicity are currently forbidden in France’s census, and the requirement for such questions in Lebanon’s census has caused it to be politically blocked since 1932). As a result, the implications of compositional shifts are virtually ignored in projections.

If these demographic twists could be captured by projections, what might they mean for the sub-Saharan African security environment? Unfortunately, it’s hard to imagine a more adverse scenario than the one currently spelled out by the UN projections.

Looking at the Youth Bulge from Another Angle

Today, 45 of sub-Saharan Africa’s 46 independent states have youthful age structures — a median age less than or equal to 25 years. These age structures cut a familiar pyramidal-shaped profile of a population with a large proportion of young adults in the working-age population (greater than or equal to 42 percent), a rapidly growing school-age population, and high rates of workforce growth, typically exceeding 3 percent per year. These qualities tend to be associated with rampant unemployment, institutional failures, and political instability.

And here’s the bad news. Unless African governments and their development partners can stimulate quick reversals in fertility trends, the passing of two decades will only slightly modify this situation. According to the UN medium-variant projection, by 2030, only Botswana, South Africa, Cape Verde, and Djibouti are expected to have matured significantly beyond this conflict-vulnerable stage of the age-structural transition, leaving sub-Saharan Africa as the remaining epicenter of the “demographic arc of instability” (see map above for 2010, and below for 2030).

Jennifer Sciubba’s criticisms, and the warnings of other political scientists and demographers, should alert policymakers that the reality could turn out to be even bleaker than current UN projections suggest. Stalling fertility transitions and ethnoreligious compositional shifts threaten to further intensify sub-Saharan Africa’s ongoing instability and prolong its countries’ vulnerabilities for decades, particularly in its western, central, and eastern sub-regions.