What are the most prominent themes in HPE research? I consider the substantive focus of approximately 200 articles published in top political science journals in the last ten years, collected for a joint review project with Eugene Finkel and Scott Gehlbach.  For additional information, check out my September post for the selection criteria and regional distribution of these studies.
Hand-coding the articles reveals the following themes as the most common in HPE research: democratization, repression and violence, legislative and party politics, state capacity, and colonialism. Below, I provide some examples and consider how these themes map onto the three uses of HPE framework introduced earlier: (1) for understanding the past for its own sake; (2) for understanding the present; and (3) as a setting to investigate general theoretical issues.
Historical democratization processes
Democratization is the most prominent theme in HPE research, at one fifth of all articles collected. (This theme is distinct from studies on the inner workings of authoritarian regimes and their resilience). Most of this work focused on understanding the past, its important contributions to the broader study of democratization notwithstanding. Scholars have used historical data to examine topics from the introduction of proto-democratic institutions to the expansion of suffrage. They draw on the theoretical foundations developed by historical institutionalist studies but use different methodological approaches.
Some HPE scholars investigate the very beginnings of democratic governance, going back to the geographic determinants of agricultural production, feudal institutions, and patterns of colonization and trade. For example, in a recent APSR article Ali Ahmed and David Stasavage locate the early origins of democracy in information asymmetries related to the lack of transparency in production. Using a dataset on the presence of council governance in 186 societies around the world, they show that councils were more likely to emerge in societies with more variable and thus less taxable agricultural production. In these settings, rulers relied on councils to gather better information about local conditions.
Other studies have focused on the introduction of institutional innovations that increased political competition and representation, such as the secret ballot, and on the expansion of suffrage. These studies compiled fine-grained subnational and roll-call data to test classic theories of democratization and develop more nuanced explanations of democratization for specific country cases. Some of their findings challenge earlier macro-historical research on the importance of economic inequality, class struggle, and human capital for democratization.
For example, Martin Ardanaz and Isabela Mares argue that shortages of agricultural workers in Imperial Prussia affected the costs of electoral intimidation and thus conservative legislators’ support for the secret ballot reform. Mona Morgan-Collins compares the de jure and de facto enfranchisement of women in the US, exploiting county-level variation in the proportion to estimate preferences of women voters. Daniel W. Gingerich shows that in Brazil, the introduction of the secret ballot resulted in suffrage restrictions, as it made it exceedingly difficult for the poor and dependent voters to participate in elections. This study also cautions against conflating contemporary functions of democratic institutions with their historical origins.
A smaller number of HPE contributions on democratization, closely related to work on colonial legacies, examine the long-run consequences of historic institutions and processes for the quality of democracy today. For example, Robert Woodberry highlights the role of Protestant missionaries in the spread of democratic norms and education, which created the conditions for democracy around the world. Tomila Lankina and Alexander Libman link communist urbanization and industrialization policies to poor democratic performance in contemporary postcommunist states.
The causes and consequences of violence and repression
Since violence and repression remain common today, the HPE toolkit is not strictly necessary for this type of inquiry. In fact, methodological challenges in understanding the effects of violence and their persistence over time arguably increase as we go deeper in history, as data becomes less available and mechanisms of persistence become harder to identify. Nevertheless, the recent HPE work on the determinants of violence and repression and on their consequences on political and economic outcomes has produced important theoretical and empirical advances.
My own fascination with HPE started with work on the enduring effects of repression and violence on political behavior, i.e. the research that uses history to understand the present. It seems intuitive that exposure to conflict changes social and economic structures and produces a lasting shift in attitudes and behaviors. HPE research has demonstrated just how lasting the consequences of violence may be.
This type of research often exploits “natural experiments” to isolate the “as if” random effect of exposure to violence. For example, Noam Lupu and Leonid Peisakhin isolate variation in the intensity of Soviet repression against Crimean Tatars, using the indiscriminate way in which some deportees died from starvation and disease due to their uprooting. They compare the descendants of deportees who lost more family members than others. A fascinating 2020 article by Erin Lin demonstrates the long-run consequences of US bombing in Cambodia on household production and welfare by exploiting the variation in unexploded ordnance that results from differences in the quality of soil. She finds that the most fertile land, where the bombs were less likely to explode, became the least productive the risk of detonation reduced individual investments and shortened time horizons.
An even larger subset of research on violence and repression studies the past for its own sake or by using history as a setting to investigate general theoretical issues. The hallmark of this type of research is the digitization of individual-level census and military records that provide information on ethnicity, socioeconomic status, participation in combat, and place of birth or residence. This work sometimes faces the tradeoff between the credibility of findings from a specific historical episode and their generalizability to contemporary conflicts and repression.
For example, Andrew Hall, Connor Huff, and Shiro Kuriwaki demonstrate the importance of slave ownership for participation in the US Civil War, using individual-level data on 3.9 million free citizens in the Confederate states. They exploit a land lottery in Georgia that increased the number of slaves owned by some households, showing that the winners’ children are more likely to serve in the Confederate Army. Benjamin Barber and Charles Miller evaluate the effectiveness of propaganda on improving German soldiers’ combat performance during World War II. They combine a random sample of army service records with information on pre-enlistment exposure to Nazi radio programming, which is plausibly exogenous to other sources of combat motivation.
Other prominent themes in HPE
Research on state capacity and related topics of clientelism and governance are another key endeavor in HPE. While early work in this tradition emphasized the role of interstate conflict, drawing on country-level datasets, more recent studies began to examine the importance of elite conflict and societal characteristics for state building. This line of inquiry became possible following the digitization of historical censuses and maps and the improvement of measurement strategies (see Pavi’s post on the conceptualization and measurement of state capacity). HPE work on state capacity is almost evenly divided: on one hand, articles that draw on history to understand the fundamental determinants of contemporary variation in the strength and presence of the contemporary state; and on the other, articles on specific historical episodes of state-building and fiscal innovation.
Many HPE studies have focused on the workings of legislatures and the development of party politics, a theme that is related to the democratization research discussed above. Studies on the introduction of proportional representation and changes in electoral rules fit this category. Other work has zoomed in on the careers of individual legislators or interrogated the development of party cohesion. Data from the US Congress and the British Parliament are commonly used in such studies.
This overview also points to the scarcity of HPE research on cultural norms, migration, identity and trade in political science journals, despite the potential of historical data and design-based inference for advancing research on these topics and prominence in economics journals. In addition, despite the importance of understanding the mechanisms of persistence for research phenomena, few studies have explicitly engaged this topic (see my review of the interdisciplinary literature on intergenerational transmission). These are promising new directions for future HPE research.
 So far, we coded 197 articles in the HPE tradition in AJPS, APSR, JOP, BJPS, World Politics, CPS, and CP.