Topic models, as developed in computer science, are effective tools for exploring andsummarizing large document collections. When applied in social science research, how-ever, they are commonly used for measurement, a task that requires careful validationto ensure that the model outputs actually capture the desired concept of interest. Inthis paper, we review current practices for topic validation in the field and show thatextensive model validation is increasingly rare, or at least not systematically reported.To supplement current practices, we refine an existing crowd-sourcing method for val-idating topic quality (Chang et al., 2009) and go on to create new procedures forvalidating conceptual labels provided by the researcher. We illustrate our method withan analysis of Facebook posts by U.S. Senators and provide software and guidance forresearchers wishing to validate their own topic models. While tailored, case-specificvalidation exercises will always be best, we aim to improve standard practices by providing general-purpose tools to validate topics as measures

  • Ying, Luwei. 2021. How State Presence Leads to Civil Conflict. Journal of Conflict Resolution, 65(2–3), 506–533.

Political scientists and policy-makers have long argued that state weakness leads to civil confl ict while enhancing state power helps prevent violence. Why, then, has increased state capacity worldwide recently coincided with more civil conflicts? This study argues that enhanced state presence at the sub-national level -- a symptom of growing state capacity -- may induce violent resistance from the established non-state powers such as local leaders and communities in the short term. Empirically, I conduct two analyses, one at the province level and the other at the ethnic group level. To measure state presence, I use accuracy of census data in the first analysis and global ground transportation data in the second analysis. Results demonstrate that increased state presence triggers civil conflict, particularly in the first five years of such increasing state presence, and this effect is stronger in remote and ethnically heterogeneous regions. Evidence also suggests that ethnic groups settled in peripheral regions are prominent resisters to state penetration. This paper thus expands prior understanding of the role of state power in civil conflicts.

  • Carter, David B. and Luwei Ying. 2021. The Gravity of Transnational Terrorism. Journal of Conflict Resolution 65(4):813-849.

Transnational terrorism is an inherently international phenomenon as it involves attacks where the perpetrators are from a different country than the victims. Accordingly, a growing literature explains patterns in transnational attacks with a focus on international variables, for example, the presence of a border wall or alliance patterns. Despite the importance of the topic, no common empirical framework with theoretical basis has emerged to analyze the flows of transnational attacks. We propose that recent versions of the structural gravity model of transnational flows, long the workhorse model in trade economics, can be modified to provide a theoretically motivated model of the flows of transnational terrorist attacks among countries. The gravity model provides several empirical advantages for the study of international variables and transnational terrorism, for example, recent specifications allow the researcher to estimate count models that condition out all time-varying country-level confounders with fixed effects. This facilitates sidestepping the typical problem that any international variables associated with transnational flows are often correlated with omitted or imprecisely measured domestic factors, which draws their estimates into question. Moreover, we demonstrate that the structural gravity model does a much better job in predicting outcomes, particularly when multiple attacks flow across borders.

Under Review

  • Historical Border Instability and Trust (with Scott F Abramson and David B. Carter), Revise and Resubmit

Recent research demonstrates historical international boundaries' long-term effects on important outcomes such as the emergence of territorial disputes and states' trading relationships. This growing literature explains these macro-level results with theory that specifies how individuals in border regions condition their behavior on border institutions in a way that persists across time. However, we lack systematic evidence of historical border institutions' effects on individuals. We argue that historical border changes have persistent effects on contemporary levels of political and social trust, with the deleterious effects of border changes on social networks being a key mechanism. We provide a battery of tests that show that historical border changes in a locality have persistent effects on contemporary levels of individual trust in political institutions and social trust in Europe. Additionally, we provide several pieces of evidence over the role that social networks play in mediating the effect of historical border changes on trust.

  • Clash of Ideologies? Evidence from US-China Competition in Voting Alignment Formation in the United Nations General Assembly (with Xun Pang)

The role of ideology in international relations has long been contentious, and the debate is currently centered on whether the US-China competition is only a contest for power or, additionally, a clash of ideologies. The challenge undertaken in this paper is to disentangle the role of ideology as a shaping factor of nation states' sincere preferences and as an instrumental tactic in international cooperation and conflict. Our research provides systemic quantitative evidence of the US-China competition via voting alignment formation in the United Nations General Assembly (UNGA). We directly model actors' preferences in this competition and integrate them into strategic interactions. We then convert the game into a Bayesian statistical estimator. Empirical evidence shows that voting alignments in UNGA fall along the "democracy-authoritarianism" division, which is a result of the competitive buy-in of the United States and China. Furthermore, we find that, apart from serving as tactical instruments for collective actions, ideologies also fundamentally shape the preferences of all parties involved: both the United States and China prefer political allies who share their values, and other states also vote based on their ideological inclinations. These findings highlight the rising concerns over a clash of ideologies between the United States and China, which have profound implications for the future world order.

Selected Working Papers

  • New “Weapon of the Weak”: Religiosity in Jihadist Propaganda

Radical religion is the dominant ideology in the most recent wave of terrorism. How do violent groups exploit this ideological "brand" in maintaining their organizations? I theorize that Jihadist propaganda is an essential component of groups' strategies, arguing that jihadi groups increase religious messaging when they face setbacks and shift towards secular messaging as their power increases. This dynamic reflects the fact that groups that are small or facing setbacks must prioritize their core members who advocate radical fundamentalism, while larger or growing groups seek broader support from more secular and less fundamentalist individuals. Empirically, I collect an original database of 121 magazines from 32 Jihadist groups from 1984 to 2019 and use a semi-supervised machine learning algorithm to scale these documents on a "religiosity - secularism" spectrum. Tying this measure to data on violent attacks, I show that the proportion of a group's rhetoric that is religious increases when groups are weaker -- a pattern holds both across groups and over time. I more precisely examine this mechanism leveraging over 18 million tweets from ISIS-related accounts in 2015. This evidence also indicates that group power influences whether groups emphasize religious or secular rhetoric depending on which audience they have incentives to reach. Thus, in sharp contrast to the prevailing view that radical jihadi ideology and violence are bound together, I demonstrate that groups put the most rhetorical emphasis on religion when they carry out fewer attacks because they are weaker.