Ethnic identities around the world are deeply intertwined with modern statehood, yet the extent to which territorial governance has shaped ethnic groups is empirically unknown. I argue that governments at the national and subnational levels have incentives to bias governance in favor of large groups. The resulting disadvantages for ethnic minorities motivate their assimilation and emigration. Both gradually align ethnic groups with administrative borders. I examine the result of this process at subnational administrative borders across Sub-Saharan Africa and use credibly exogenous, straight borders for causal identification. I find substantive increases in the local population share of administrative units' predominant ethnic group at units’ borders. Powerful traditional authorities and size advantages of predominant groups increase this effect. Data on minority assimilation and migration show that both drive the shaping of ethnic groups along administrative borders. These results highlight important effects of the territorial organization of modern governance on ethnic groups.

This paper uses the gradual expansion of the European railway network to investigate how this key technological driver of modernization affected ethnic separatism between 1816 and 1945. Combining new historical data on ethnic settlement areas, conflict, and railway construction, we test how railroads affected separatist conflict and successful secession as well as independence claims among peripheral ethnic groups. Difference-in-differences, event study, and instrumental variable models show that, on average, railway-based modernization increased separatist mobilization and secession. These effects concentrate in countries with small core groups, weak state capacity, and low levels of economic development as well as in large ethnic minority regions. Exploring causal mechanisms, we show how railway networks can facilitate mobilization by increasing the internal connectivity of ethnic regions and hamper it by boosting state reach. Overall, our findings call for a more nuanced understanding of the effects of European modernization on nation building.

Borders define states, yet little systematic evidence explains where they are drawn. Putting recent challenges to state borders into perspective and breaking new methodological ground, this paper analyzes how ethnic geography and nationalism have shaped European borders since the 19th century. We argue that nationalism creates pressures to redraw political borders along ethnic lines, ultimately making states more congruent with ethnic groups. We introduce a Probabilistic Spatial Partition Model to test this argument, modeling state territories as partitions of a planar spatial graph. Using new data on Europe's ethnic geography since 1855, we find that ethnic boundaries increase the conditional probability that two locations they separate are, or will become, divided by a state border. Secession is an important mechanism driving this result. Similar dynamics characterize border change in Asia but not in Africa and the Americas. Our results highlight the endogenous formation of nation-states in Europe and beyond.

Many European nation-states were historically homogenized through violent ethnic cleansing. Despite its historical importance, we lack systematic evidence of the conditions under which groups where targeted with cleansing and how it impacted states' ethnic demography. Rising nationalism in the 19th century threatened multi-ethnic states with right-sizing through secessionism and irredentism. States therefore frequently turned to brutal right-peopling, in particular where cross-border minorities and those with a history of political independence increased the risk of territorial losses. We test this argument with new spatial, time-variant data on ethnic geography and ethnic cleansing from 1886 to the present. We find that minorities that politically dominated another state and those that have lost political independence were most at risk of ethnic cleansing, especially in times of interstate war. At the macro-level, our results show that ethnic cleansing increased European states' ethnic homogeneity almost as much as border change. Both produced today's nation-states by aligning states and ethnic nations.

How do Ukrainians view the costs and benefits of armed self-defense? We examine support for different strategies Ukraine could pursue against Russia, using a conjoint survey experiment with 1,160 Ukrainian respondents, fielded in July 2022. The strategies have projected outcomes with varying degrees of political autonomy and territorial integrity and three expected costs: civilian fatalities, deaths among Ukrainian fighters, and risk of nuclear escalation. We find that Ukrainians strongly prefer strategies that fully restore Ukraine's political autonomy and territorial integrity, even if concessions would reduce the costs of fighting Russia. The moral principle of proportionality suggests that the expected costs of self-defense should not exceed its projected benefits, corresponding to calls on Ukraine to grant concessions to end the war. Our respondents' choices do not reflect this logic. Instead they evoke a categorical resistance against aggression: 79 percent of respondents oppose strategies leading to a Russian-controlled government, regardless of the costs.

The recent revival of nationalism has brought a threatening return of revisionist conflict. Yet, because of its radically modernist orientation dismissing past references as irrelevant, current scholarship on nationalism and political violence offers little guidance. Taking the nationalists seriously if not literally, we study how they use narratives harking back to past 'golden ages' to legitimize territorial claims and mobilize resources for action in post-Napoleonic Europe. Our analysis draws on geocoded data on state borders going back to the Middle Ages, combined with new spatial data on ethnic settlement areas from the 19th century retrieved from historical atlases. Our findings indicate that restorative nationalism, conceptualized as a loss of power and/or unity relative to past reference points, increases the risk of civil and interstate conflict.

To what degree and why are traditional institutions persistent? Following up on the literature on the long-term effects of precolonial institutions in Africa, we investigate whether and where today's traditional institutions mirror their precolonial predecessors. We do so by linking data on contemporary traditional institutions of African ethnic groups with Murdock's historical Ethnographic Atlas. We find a robust association between past and present levels of institutional complexity, differentiating between institutions' political centralization and functional differentiation. However, this persistence originates almost exclusively from former British colonies governed with more reliance on precolonial institutions than other colonies, in particular French ones. These findings contribute to research on the development and effects of traditional institutions, highlighting the need to account for varying persistence of traditional institutions.

Having increased for centuries, territorial state size began to decline toward the end of the nineteenth century and has continued to do so. The authors argue that processes triggered by ethnic nationalism are the main drivers of this development. Their empirical approach relies on time-varying spatial data on state borders and ethnic geography since the nineteenth century. Focusing on deviations from the nation-state ideal, the authors postulate that state internal ethnic fragmentation leads to reduction in state size and that the cross-border presence of dominant ethnic groups makes state expansion more likely. Conducted at the systemic and state levels, the analysis exploits information at the interstate dyadic level to capture specific nationalist processes of border change, such as ethnic secession, unification, and irredentism. The authors find that although nationalism exerts both integrating and disintegrating effects on states' territories, it is the latter impact that has dominated.

Prominent arguments hold that African states' geography limits state capacity, impedes public service provision, and slows economic development. To test this argument, I collect comprehensive panel data on a proxy of local state capacity, travel times to national and regional capitals. These are computed on a yearly 5x5km grid using time-varying data on roads and administrative units (1966-2016). I use these data to estimate the effect of changes in travel times to capitals on local education provision, infant mortality rates, and nightlight emissions. Within the same location, development outcomes generally improve as travel times to its capitals decrease. These data and results improve the measurement of state capacity and contribute to the understanding of its effects on human welfare. <br /><br /> The data are available on this [Github page](https://github.com/carl-mc/state_reach_africa).

Social scientists increasingly combine multiple datasets to study ethnicity in Africa. We facilitate these efforts by systematically linking over 8'100 ethnic categories from eleven databases including surveys, geographic data, and expert-coded lists. Exploiting the linguistic tree from the Ethnologue database, we propose a systematic solution to the *grouping problem* of ethnicity. Novel empirical results on trust in African heads of states highlight the importance of explicitly considering sample inclusion criteria and different ways of linking ethnic categories from multiple datasets. An R-package allows researchers to link ethnic groups from any database with explicit rules and to easily add their own data on ethnic groups.

How does local ethnic demography affect the conduct of majoritarian elections? Because legislative elections in majoritarian systems are contested locally, local ethno-political polarization increases the risk of pre-election violence. In districts that are polarized between politically competing ethnic groups, violence can be targeted with comparative ease at opposing voters, and can, if perpetrated collectively, mobilize the perpetrators' co-ethnics. I expect no such dynamics in PR systems where political competition plays out at higher geographical levels. To test this argument, I combine new data on the ethnic composition of local populations in 22 African countries with monthly data on riots and survey data on campaign violence. Ethno-politically polarized districts in majoritarian and mixed electoral systems see substantively larger increases in the number of riots prior to legislative elections and more fear of pre-election violence among citizens than non-polarized districts in the same country and at the same time. I do not find these patterns in PR systems. The results enhance our understanding of how electoral systems interact with local ethnic demography in shaping pre-election violence.

This article investigates how local ethnic demography affects strategies of favoritism in Africa. Recent studies of ethnic favoritism report advantages of either presidents' ethnic peers or home regions. As regions in multi-ethnic states are rarely perfectly homogeneous, these studies cannot disentangle whether favoritism targets entire regions or co-ethnic individuals. We argue that governments' provision of goods depends on local ethnic demographies. Where government co-ethnics are in the majority, ethno-regional favoritism benefits all locals regardless of their ethnic identity. Outside of these strongholds, incumbents pursue discriminatory strategies and only their co-ethnics gain from favoritism. We use fine-grained geographic data on ethnic demography and infant mortality to test these hypotheses. Results from rigorous fixed effects specifications that exploit temporal changes in the ethnic composition of governments support our theoretical claims. Our findings have important implications for theories of distributional politics and conflict in multi-ethnic societies.

Weak state capacity is one of the most important explanations of civil conflict. Yet, current conceptualizations of state capacity typically focus only on the state while ignoring the relational nature of armed conflict. We argue that opportunities for conflict arise where relational state capacity is low, that is, where the state has less control over its subjects than its potential challengers. This occurs in ethnic groups that are poorly accessible from the state capital, but are internally highly interconnected. To test this argument, we digitize detailed African road maps and convert them into a road atlas akin to Google Maps. We measure the accessibility and internal connectedness of groups via travel times obtained from this atlas and simulate road networks for an instrumental variable design. Our findings suggest that low relational state capacity increases the risk of armed conflict in Africa.

Low levels of development and state capacity in Africa are thought to originate in colonialism in general and indirect colonial rule in particular. But despite a century of debate about the nature, causes, and consequences of direct and indirect colonial rule on the continent, data and evidence about its application are scarce. Based on newly collected historical data, this paper provides evidence for two claims that have marked the debate since its inception. First, British administrations have ruled more indirectly than French ones. French colonization led to demise of 7 out of 10 pre-colonial polities. Under British rule, 3 out of 10 polities disappeared as measured by the continuation of their lines of succession. Second, pre-colonial centralization was a crucial prerequisite for indirect rule. Local administrative data from 8 British colonies shows that British colonizers employed less administrative effort and devolved more power to native authorities where centralized institutions existed. Such a pattern did not exist in French colonies. Together, these findings improve our understanding of the long-term effects of pre-colonial institutions, the roots of regional and ethnic inequalities, and the origins of currently observed customary institutions in Africa.

Research on ethnic politics and political violence has benefited substantially from the growing availability of cross-national, geo-coded data on ethnic settlement patterns. However, because existing datasets represent ethnic homelands using aggregate polygon features, they lack information on ethnic compositions at the local level. Addressing this gap, this article introduces the Spatially Interpolated Data on Ethnicity (SIDE) dataset, a collection of 253 near-continuous maps of local ethno-linguistic, religious, and ethno-religious settlement patterns in 47 low- and middle-income countries. We create these data using spatial interpolation and machine learning methods to generalize the ethnicity-related information in the geo-coded Demographic and Health Surveys (DHS). For each DHS survey we provide the ethnic, religious, and ethno-religious compositions of cells on a raster that covers the respective countries at a resolution of 30 arc-seconds. The resulting data are optimized for use with geographic information systems (GIS) software. Comparisons of SIDE with existing categorical datasets and district-level census data from Uganda and Senegal are used to assess the data's accuracy. Finally, we use the new data to study the effects of local polarization between politically relevant ethnic groups, finding a positive effect on the risk of local violence such as riots and protests. However, local ethno-political polarization is not statistically associated with violent events pertaining to larger-scale processes such as civil wars.

Itinerant rule, rule exercised through traveling, was a common, yet barely studied pre-modern form of governance. Studying the determinants of ruler itineraries in the Holy Roman Empire AD 919-1519, we argue that rulers focused on monitoring 'marginal' elites. Powerful rulers could count on family members and thus targeted unrelated local elites. Weak emperors had to monitor their less loyal relatives and left unrelated nobles unvisited. We reconstruct emperors' itineraries from 72'665 dated and geolocated documents and measure territorial control by their relatives. Exploiting the weakening of imperial power through the Great Interregnum (1250-1273), we find that strong, pre-1250 emperors frequented areas controlled by their relatives relatively less. In contrast, family control increased visits post-1273. Causal identification rests on the discontinuous reduction of emperors' power through the Great Interregnum and differences in family relations between subsequent emperors. The results show strategic itinerant rule as an important yet understudied form of governance.

War-affected populations are often divided along social identities as well as by individuals' difficult choices of fighting for either side or keeping their head down. Focusing on Ukraine, we study the question of whether Ukrainians now primarily relate to each other based on fated traits like ethnic descent or their choices to resist or collaborate with Russia. We articulate alternative psychological and moral theories about whether a war of national survival should harden ethnic divisions or create pressure to accept individuals based on their choices. Relying on interviews and two conjoint experiments, we find that Ukraine's citizens prefer neighbors who resist Russia's aggression in line with the moral theory. However, ethnic descent is a psychological barrier to integration as citizens prefer a passive Ukrainian over a Russian who resisted. Our findings reveal challenges to social cohesion in Ukraine.

This note replicates and extends a conjoint survey experiment on Ukrainians' attitudes toward the costs and benefits of self-defense against Russia's aggression, conducted in July 2022 (Dill, Howlett and Müller-Crepon, 2024). Between December 2024 and January 2025, we presented the original and a modified experiment with stronger cost treatments to 2,580 Ukrainian citizens, sampled from largely the same locations as in 2022. We find continued categorical resistance to Russian control. Resistance to accepting political neutrality or conceding territory meanwhile has weakened. Ethnic Ukrainians, less war-affected respondents and those more trusting in Ukraine's president are comparatively more willing to resist Russia's aggression. Locations' exposure to the war is not associated with changes in Ukrainians' attitudes. Our findings help us better understand how the attitudes of conflict-affected populations evolve over time and shed light on public support for a potential political settlement in Ukraine.

Ethnicity is an important political cleavage in Africa, yet the degree of its influence on voting is contested. Selection biases from restricted choice sets complicate micro-level analyses, while bias from ecological inferences and unobserved confounders hamper meso and macro-level approaches. We develop the *Co-Voting Regression* (CVR) model to tackle these challenges. It estimates the effect of co-ethnicity on the probability that pairs of voters co-vote for the same party/candidate while conditioning on other characteristics that connect voters. In doing so, CVR mirrors the micro-foundations of widely-used aggregate indicators, such as the effective number of parties and the Herfindahl-Hirschman index of ethnic homogeneity. Our data consists of dyadic comparisons between respondents from Afrobarometer surveys. Pooling across 28 countries, our results show that co-ethnicity increases co-voting intentions by 16 percentage points. The effect of co-ethnicity is consistent across institutionally diverse countries and at least five times larger than that of other cleavages. Beyond ethnicity, the approach we propose addresses key methodological concerns in studies of the electoral consequences of socio-economic cleavages and bridges gaps between levels of analysis.

The design of subnational administrative units is fundamental to the functioning of states and their political topography. Yet, we lack theoretical and empirical knowledge on the determinants of the partitioning of state territories into subnational governance units. I argue that aligning administrative borders with ethnic geography facilitates local institutional persistence and increases short term governance efficiency. Yet, because such *packing* of units stabilizes peripheral institutions and identities, some governments may instead design heterogeneous units and *crack* groups and their institutions to centralize power. I analyze these arguments by studying unit-design in Sub-Sahara Africa, contrasting indirect with direct forms of colonial rule using new data on administrative and early-colonial ethnic geographies derived from historical maps. Modeling administrative borders with a probabilistic spatial partition model, I find evidence that administrative borders are strongly and positively associated with ethnic boundaries. These effects are more pronounced under indirect British compared to more direct French rule and driven by their packing of uncracked groups into administrative units. With novel theory, data, and methods, this paper contributes to our understanding of the varying ethno-geographic roots of administrative geographies in Africa.

Nature protected areas are hailed as an institutional solution to the global biodiversity crisis. However, conservation entails local economic costs for some communities and benefits for others. We propose that the establishment of protected areas in Africa follows an ethno-political logic which implies that governments distribute protected areas such that their ethnic constituencies are shielded from their costs but enjoy their benefits. We test this argument using continent-wide data on ethnic groups’ power status and protected area establishment since independence. Difference-in-differences models show that political inclusion decreases nature protection in groups' settlement areas. Yet, this effect is reversed for protected areas that plausibly generate tourism income. We also find that ethno-political inclusion is linked to legal degradation of protected areas. Our findings on the ethno-political underpinnings of nature protection support long-voiced concerns by activists that politically marginalized groups carry disproportional costs of nature conservation.

Colonial governance in Africa varied considerably in its extent of indirect rule through precolonial institutions. Assessing the developmental consequences of indirect rule, this paper argues that it strengthened populations' bargaining power and increased public service provision in return for taxation of agricultural produce, in particular cash crops. To test this argument, I exploit variation in the indirectness of colonial rule -- whereas British indirect rule increased in the centralization of precolonial institutions, the French implemented more uniform direct rule. I furthermore measure public service provision with geo-referenced education outcomes of individuals born and raised under colonial rule and use soils' suitability for cash crop production as an exogenous proxy for real production. Supporting the theoretical claim, the effect of cash crop suitability on primary education increases with precolonial centralization in former British colonies, but not in French ones. Comparisons of education rates in neighboring ethnic groups with different levels of centralization and ethnic groups cut by British-French boundaries reaffirm this result. Contemporary development outcomes show patterns consistent with persistent effects of indirect rule in cash crop producing areas. The findings underscore the joint importance of political institutions and resource endowments in determining local development.