Geospatial Analysis of Ethnic Diversity, Political Geography, and Electoral Patterns in South West Nigeria

The intersection of ethnic geography and electoral patterns in Nigeria's South West geopolitical zone offers important insights into the spatial determinants of voting behaviour, political competition, and democratic consolidation in a multiethnic federal democracy characterised by significant sub-regional linguistic and cultural heterogeneity within the Yoruba homeland. This study conducts a geospatial analysis of ethnic diversity distribution, constituency delimitation, and electoral outcome patterns in South West Nigeria covering the 2019 and 2023 general elections. Ethnolinguistic group distribution data were estimated from community enumeration records, linguistic atlas data, and National Population Commission ward-level census derivatives. Electoral outcome data from the Independent National Electoral Commission were geocoded to constituency level and linked to demographic and socioeconomic indicators from NBS datasets. Spatial regression modelling using Spatial Lag and Spatial Error specifications was applied to test whether ethnic diversity indices predict inter-constituency variation in vote margins, party competition, and voter turnout, controlling for income, urbanisation, and incumbency effects. Results indicate that ethnic diversity within constituencies is positively associated with electoral competitiveness and vote splitting across party lines, while ethnically homogeneous constituencies show more predictable voting patterns aligned with dominant group party preferences. The geopolitics of constituency boundary delimitation shows systematic bias toward over-representing rural constituencies relative to urban ones in Ogun and Oyo States. This study makes an original methodological contribution by applying spatial econometric techniques to electoral geography analysis in South West Nigeria, advancing a literature previously dominated by non-spatial approaches. Keywords: electoral geography, ethnic diversity, South West Nigeria, spatial analysis, political geography.