African polygamy over space
I map African polygamy in Figure 1. Each point is a married woman for whom the DHS data gives geographic coordinates. Red dots are polygamists, while blue dots are monogamists. Polygamy is most concentrated in West Africa, though it really is in no way limited there. Polygamy in the info is basically bigamy – 72% of respondents report they are the only wife, 19% report that their husband has two wives, 7% report that he has three wives, and less than 2% report that he has 4 wives or even more.
Figure 1 . Polygamy in Africa
The three hypotheses I test about the spatial distribution of polygamy relate with geographic, historical, and cultural variables that are slow to improve. First, Jacoby (1995), building on Boserup (1970), has linked differences in the demand for wives across parts of the Ivory Coast to the productivity of ladies in agriculture. I find, in comparison, that polygamy is least common in those elements of Africa where women have historically been most significant in agriculture. Second, economists since Becker (1974) have argued that polygamy can only just exist where there is inequality between men. I am unable to find any correlation between wealth inequality recorded in the DHS and the probability a woman is polygamous. I find, however, that historical inequality predicts polygamy today. Similarly, geographic predictors of inequality which have been found in other studies also predict the existence of polygamy in today’s. Third, I confirm the consequence of Dalton and Leung (2013) that greater slave-trade exposure predicts polygamy today. I add the caveat, however, that the effect stems largely from the broad contrast of West Africa to all of those other continent.
African polygamy as time passes
I show the decline of polygamy as time passes for an array of countries in Figure 2. A raw correlation between year of birth and polygamy will confound time trends with age effects, since a lone wife may later turn into a polygamist’s senior wife. Thus, I estimate time trends through the use of countries which have multiple DHS surveys, regressing polygamy on quartic polynomials in age and year of birth.
Figure 2 . Predicted polygamy by year of birth for 30-year-old women
I calculate the predicted probability a woman aged 30 is polygamous as a function of her year of birth. I present sample trends in Figure 2. In the paper, I show similar trends for all countries where the data permit this. Although speed of the decline has differed across countries, its presence has been widespread.
The six hypotheses I test which have the potential to describe these trends examine time-varying factors that may influence polygamy. First, I exploit two natural experiments which have increased female education in Nigeria and Zimbabwe, and discover no causal aftereffect of women’s schooling on polygamy. In comparison, I take advantage of data on colonial teachers and missions from Huillery (2009) and Nunn (2011) showing that areas that received more colonial-era educational investment show lower degrees of polygamy in today’s.
Second, I take advantage of exogenous variation in country-level rainfall to predict country-level incomes over a woman’s adolescence that typically precede her marriage. These subsequently predict lower rates of polygamy. Third, I show a similar pattern exists at the neighborhood level. Adverse local rainfall shocks experienced in a woman’s adolescent years make her much more likely to marry a polygamist. Fourth, conflict exposure at the neighborhood level acts just like a detrimental rainfall shock, increasing the prevalence of polygamy among adolescent girls subjected to it. Both these effects, however, are small.
Fifth, I take advantage of a regression discontinuity design to check for breaks in the prevalence of polygamy across national borders. With a few exceptions, I find that polygamy largely passes smoothly over borders, demonstrating that national bans and other policies have already been mostly ineffective. Last, I take advantage of a country-level differences-in-differences approach and an all natural experiment from Uganda to check whether declining child mortality predicts reduced polygamy rates, and discover a big effect.
These results pose challenges to existing theories of polygamy. The distribution of polygamy in Africa will not fit a conclusion rooted in the gender division of labour. I find no evidence that educating ladies in today’s reduces polygamy. Further, I find that history matters. Pre-colonial inequality, the slave trade, and colonial education all predict polygamy rates in today’s. I find limited evidence that African marriage markets have taken care of immediately economic growth and fluctuations. The biggest elasticities that I find are in response to changes in child health. That is in keeping with theories that see polygamy as a technique for men to improve fertility, making wives and surviving births per wife substitutes.
Becker, G (1974), “A Theory of Marriage: Part II”, in Theodore W Schultz (ed.), Marriage, Family, Human Capital, and Fertility: 11-26.
Boserup (1970), Woman’s role in economic development, NY: Martin’s Press.
Dalton, J and T Leung (2013), “How come polygyny more frequent in Western Africa? An African slave trade perspective”, forthcoming in Economic Development and Cultural Change.
Edlund, L and N-P Lagerlöf (2006), “Individual versus parental consent in marriage: Implications for intra-household resource allocation and growth”, The American Economic Review 96(2): 304-307.
Edlund, L and N-P Lagerlöf (2012), “Polygyny and its own Discontents: Paternal Age and Human Capital Accumulation”, working paper.
Fenske, J (2013), “African Polygamy: Past and Present”, CSAE Working Paper WPS/2012-20.
Huillery, E (2009), “History matters: The long-term impact of colonial public investments in French West Africa”, American Economic Journal: Applied Economics 1(2): 176-215.
Jacoby, H (1995), “The economics of polygyny in Sub-Saharan Africa: Female productivity and the demand for wives in Côte d’Ivoire”, Journal of Political Economy 103(5): 938-971.
Nunn, N (2011), “Gender and Missionary Influence in Colonial Africa”, forthcoming in African Poverty of the Longue Durée.
Tertilt, M (2005), “Polygyny, fertility, and savings”, Journal of Political Economy 113(6): 1341-1374.
1 ‘Polygamy’ here refers exclusively to polygyny (multiple wives). Polyandry (multiple husbands) is uncommon everywhere.