This study traces how two major nineteenth- and twentieth-century transformations—export agriculture (cash crops) and print technologies—helped produce the ethnic landscapes of contemporary African states. Using a preregistered research design, the analysis tests whether these forces changed ethnic politicization and the making of group boundaries.

📚 How historical exposure was measured

• Historical data on cash crop endowments capture the spread of export agriculture and its potential to generate agricultural rents and mobilization.
• Records of African-language publications capture the diffusion of print technologies and their role in spreading shared texts and communication.
• These historical exposures are linked to postindependence outcomes for ethnic groups and to individual reports of ethnic identity salience.

🔎 Key findings

• Groups with historical exposure to cash crops or print technologies are more likely to be politically relevant in the postindependence period.
• Members of exposed groups report stronger, more salient ethnic identities.
• Effects on boundary-making differ by mechanism: cash crop exposure increased groups’ mobilizational potential while producing more exclusionary boundaries aimed at controlling agricultural rents.
• By contrast, print exposure strengthened imagined communities and produced ethnic identities that were more salient but relatively porous; printing fostered greater openness to assimilate linguistically related outsiders as measured by interethnic marriage.

🧭 Why this matters

These results identify historical sources of ethnic politicization and clarify mechanisms that shape how group boundaries form—showing that economic and communication revolutions can both politicize ethnicity but with contrasting implications for openness and exclusion.