I begin the book by providing an overview of recent political economy literature on ethnicity, which largely assumes that ethnicity is fixed and unchanging despite decades of evidence to the contrary. I then introduce my argument as an attempt to explain ethnic change. I first argue that people hold multiple ethnic identities simultaneously, and that individuals emphasize the one that brings them the most benefits. I then build upon earlier theories from Marx and Gellner to claim that industrialization is the most powerful factor that leads people to re-identify with larger ethnic groups, and that this process of assimilation is induced by the decline in the relative value of land. Inasmuch as the process of industrialization is inherently uneven, however, I suggest that assimliation should proceed unevenly as well. Finally I claim that the major role played by states in my theory is in their ability to promote or inhibit industrialization, not through assimilationist policies. I then go on to establish the scope conditions of my argument, namely the way I focus on ethnic change in non-violent contexts while also limiting myself to non-immigrant communities.

Finally, in Chapter 10 I close the book by discussing some broader conclusions about the study of ethnicity and ethnic change, while also speculating about future prospects for the relationship between industrialization and assimilation. In the former case I focus on such topics as future quantitative work using data on ethnicity, our understanding of individuals who change their ethnic identities, the role of the state in enforcing or promoting ethnic identification and policy implications as regards promoting industrialization. In the latter case I return to my original dataset of country censuses from Chapter 4 to see if the relationship between industrialization and ethnic diversity changes over time. Upon introducing an interaction effect, I find evidence for a declining effect over time, although it appears that the interaction effect is driven by observations from the Americas, a result for which I find evidence in the secondary literature as well.

Here I provide an overview of the concepts of ethnicity and industrialization. I first define ethnic groups as descent-based groups and show how vertical ethnic change can take place, both through the consolidation of smaller ethnic groups into larger ones as well as assimilation into a national identity. The chapter also discusses why the book focusses on what I call vertical ethnic change instead of horizontal ethnic change, namely because the former is far more prevalent than the latter. I then provide a similar overview of the concept of industrialization, by focussing on how industrialization has historically involved a shift in the focus of the economy from rural agriculture to urban employment and from land to labour as the predominant factor of production. I justify my use of carbon emissions as my predominant cross-national quantitative measure of industrialization and my use of urbanization as my main proxy for industrialization for regions or communities within countries.