Pre-colonial institutions in sub-Saharan Africa continue to exert a powerful influence on current outcomes. For example, women whose ethnic groups regularly practiced polygamy before colonial rule are more likely to be in polygamous marriages today. Children born in ethnic groups where slavery was widespread in the past receive fewer vaccinations today. And land is more likely to be acquired through commercial transactions today in places where the nuclear family''s control of land was strong in the past.


These are among the findings of research by James Fenske, published in the December 2013 issue of the Economic Journal. His study merges George Murdock''s Ethnographic Atlas – a huge database on world cultures – with multiple sources of spatial data to test the extent to which geographical features predict patterns of land rights, slavery and population density.


He notes that on the eve of colonial rule, slavery was widespread in Africa. Land tenure on much of the continent was, and still is, characterised by group rights and overlapping claims. Historians such as Gareth Austin have linked these facts to Africa''s relatively low population density. Since land was not scarce, rights over it were ill-defined. Because independent farmers could not be persuaded to become hired workers, coerced and household labour were more prevalent than wage employment.


The new study shows that land rights and slavery are both correlated with the geographical features of the ethnic groups that practice them. Notably, the groups in the sample are more likely to possess rights over land if land quality is better. Within Africa, there is a positive correlation between land quality and slavery but this does not hold in the full global sample.


Many of the correlates of institutions and population density that predict differences across continents cannot explain differences across societies within a given continent, and the correlates of institutions within Africa differ from those in the full sample.


Influential theories of land rights emphasise population pressure and the market value of output as key determinants of property institutions. The new results suggest that rights existed historically where land was scarce and valuable, though there is only mixed evidence that access to trade was a determining factor.


The most widely accepted theories of slavery focus on labour scarcity, workers'' outside options and the productivity of slavery in specific tasks. The new results suggest that slavery evolves with time alongside population. They do not offer unqualified support for any particular theory of slavery.


Fenske shows that pre-colonial institutions predict institutional outcomes in Africa in the present, including land transactions, polygamy and public goods. He compares Ghanaian ethnic groups in which a child could inherit a parent''s land with groups in which land could pass out of the nuclear family through inheritance. Where the nuclear family was strong in the past relative to the wider lineage, land is more likely to be acquired through commercial transactions today.


''Does Land Abundance Explain African Institutions?'' by James Fenske is published in the December 2013 issue of the Economic Journal. James Fenske is at the University of Oxford.