Horizontal versus vertical inequalities: the relative significance of geography versus class in mapping subnational fertility
Authors: Benoit Kalasa, Parfait Eloundou-Enyegue, Sarah C Giroux
Journal: The Lancet Global Health (2021)

When studying global variation in fertility rates, researchers usually focus on one of two tracks. The first track, as taken by Carla Pezzulo and colleagues in the subnational analysis published in The Lancet Global Health,1Pezzulo C et al.Geographical distribution of fertility rates in 70 low-income and middle-income countries, 2010–16: a subnational analysis of cross-sectional surveys.Lancet Glob Health. 2021; 9: e802-e812Summary Full Text Full Text PDF Scopus (6) Google Scholar emphasises geographic variation and the tendency for high fertility to cluster spatially. This spatial, or horizontal, clustering is presumably driven by culture and social structure, including the availability of family planning infrastructure. The geographic clustering of fertility was first observed across Europe in the 19th century, and was due to cultural and linguistic boundaries between regions, which shaped the spread of information and innovative behaviour.2Coale AJ Watkins SC The Decline of Fertility in Europe. Princeton University Press, Princeton1986Google Scholar Similarly, Pezzulo and colleagues find current geographic clustering of fertility rates across low-income and middle-income countries as these countries advance in their fertility transitions. Other researchers of fertility rates focus their work on socioeconomic inequality within geographic units; the vertical track. Some scholars have questioned whether the poor increasingly bear a disproportionate share of national reproduction.3Eloundou-Enyegue P Giroux S Tenikue M African transitions and fertility inequality: a demographic kuznets hypothesis.Popul Dev Rev. 2017; 43: 59-83Crossref Scopus (13) Google Scholar If they do, fertility transitions might spur a vicious cycle of economic and reproductive inequality. Indeed, one finds a steep economic gradient in fertility across all countries in the Pezzulo study, with fertility rates in the bottom wealth quintile being twice as high as in the top quintile.4ICFThe DHS program STATcompiler.http://www.statcompiler.comDate: 2021Date accessed: March 11, 2021Google Scholar The driving force behind this vertical clustering is neither social structure or culture, but economic circumstance. Since both types of fertility inequality exist, why should analysts focus on one instead of the other? Are they truly distinct? If so, can the inequalities be integrated? Interestingly, the horizontal and vertical perspective share the same initial purpose; to recognise in-country heterogeneities that are masked when examining only national-level data.1Pezzulo C et al.Geographical distribution of fertility rates in 70 low-income and middle-income countries, 2010–16: a subnational analysis of cross-sectional surveys.Lancet Glob Health. 2021; 9: e802-e812Summary Full Text Full Text PDF Scopus (6) Google Scholar However, the two perspectives quickly diverge over which heterogeneity to reveal and which one to keep masking, and also over policy implications. Carla Pezzulo and colleagues draw much-needed attention to spatial inequalities in fertility within countries, but do not address fertility inequalities across classes. This exclusively geographic lens logically leads to recommend targeting high fertility cluster areas to increase contraceptive prevalence.1Pezzulo C et al.Geographical distribution of fertility rates in 70 low-income and middle-income countries, 2010–16: a subnational analysis of cross-sectional surveys.Lancet Glob Health. 2021; 9: e802-e812Summary Full Text Full Text PDF Scopus (6) Google Scholar In this study, physical access not economic access, is deemed the limiting factor in fertility equality, and planners can meet the pending demand for contraceptive services simply by reducing the distance to health centres. From this perspective, fertility "hot spots" can also be described as empty spots, with no fertility infrastructure but much demand. Certainly, it makes practical sense to fill these empty spots and to base fertility programming on the geography of unmet demand. It also seems ethical to find a balance in the creation of fertility support infrastructure, consistent with the ideals of voluntary participation and meeting unmet needs; build, and they will come. However, many reviews of fertility and health interventions show supply to be necessary for creating equality but that supply is insufficient on its own.5Hecht R Poirrier C Rowland M Tolmie C Accelerating progress in family planning: options for strengthening civil society-led monitoring and accountability. Results for Development Institute, Washington, DC2014Google Scholar To be effective, demand must be backed by purchasing power. Otherwise, services are physically accessible but economically inaccessible. For this reason, the inclusive approach to universal health care usually goes beyond programme coverage (supply) to include population coverage as well. In fact, economic access can sometimes supersede physical access. For instance, even if local services are poor, wealthier families can afford to travel a few miles to reach better services. Even when physical and financial barriers are overcome, discriminatory practices may suppress the utilisation of health-care services; as a United Nations Population Fund commissioned report noted, one in three women report being mistreated by health workers when they go for family planning services.5Hecht R Poirrier C Rowland M Tolmie C Accelerating progress in family planning: options for strengthening civil society-led monitoring and accountability. Results for Development Institute, Washington, DC2014Google Scholar This type of mistreatment is most common among the poor and less educated.6Sully EA et al.adding it up: investing in sexual and reproductive health 2019.https://www.guttmacher.org/report/adding-it-up-investing-in-sexual-reproductive-health-2019Date: July 2020Date accessed: March 11, 2021Google Scholar Again, supply is not a sufficient response to fertility inequality, and nor is demand. An effective response must combine supply and demand, in other words, both horizontal and vertical dimensions of fertility inequality. For policymakers, this means creating programmes that address inequalities in supply (infrastructure) and demand (perhaps through cash transfers). For researchers, this dual approach raises the methodological question of how to simultaneously track these two dimensions. Since not all inequalities are equal,7Sully EA Biddlecom AS Darroch JE Not all inequalities are equal: differences in coverage across the continuum of reproductive health services.BMJ Glob Health. 2019; 4e001695Crossref PubMed Scopus (11) Google Scholar scholars must assess how the relative salience of these complementary forms of inequality changes over time.8Firebaugh G Goesling B Accounting for the recent decline in global income inequality.Am J Sociol. 2004; 110: 283-312Crossref Scopus (111) Google Scholar Here, research on fertility inequality can be guided by principles from the broader literature on economic inequality. After decades of fierce and often silly wrangling over the nature of global economic trends,9Birdsall N That silly inequality debate.Finance Dev. 2002; 38: 92-94Google Scholar this literature has come to agree on two key points. First, the significance of various factors (class, geography, race, and gender) must be expected to change over time. Second, global inequality is best understood by integrating within-country components and between-country components. This integration of geography and class is possible and can be achieved by creative decomposition of global trends in terms of their spatial and class components. Analyses of these components can build on the geographic clusters defined by Carla Pezzulo and colleagues, but also should consider social inequality and use formulae that have been proposed for decomposable measures of inequality.10Eloundou-Enyegue P Giroux S Tenikue M African transitions and fertility inequality: a demographic kuznets hypothesis.Popul Dev Rev. 2017; 43: 59-83Crossref Scopus (8) Google Scholar By so doing, researchers can help policymakers refine programme targeting in ways that acknowledge both horizontal and vertical inequalities. A key principle of the UN's 2030 agenda is to leave no one behind, and this means serving both the places and the people left behind. We declare no competing interests. Geographical distribution of fertility rates in 70 low-income, lower-middle-income, and upper-middle-income countries, 2010–16: a subnational analysis of cross-sectional surveysSubstantial within-country variation in the distribution of fertility rates highlights the need for tailored programmes and strategies in high-fertility cluster areas to increase the use of contraception and access to secondary education, and to reduce unmet need for family planning. Full-Text PDF Open Access