This study examines the role of climate change in shaping return migration intentions among international migrants. Using an original representative survey of over 1000 first-generation West African migrants in Germany, we correlate variation in climate conditions in respondents' subnational regions of origin in West Africa to their return migration intentions. We also embed a survey experiment to test whether informational cues about future climate disasters in migrants' origin countries affect their desire to return home. We find no evidence that observed climate conditions correlate with return migration intentions, nor that experimentally manipulated climate disaster cues causally affect these intentions. Moreover, we find that differences in migrants' socioeconomic status, education or attachment to their home countries do not moderate the influence of climate conditions on return intentions. By contrast, economic cues in the experiment play a decisive role: migrants are more inclined to return when job prospects in their home country are favourable, whereas having a good job in Germany reduces return intentions. These results suggest that, in this setting, economic motivations are more salient than environmental concerns in shaping return migration intentions.

The discourse on human trafficking often depicts migrants as deceived victims, while alternative accounts view trafficking as a constrained migration strategy. We contribute to this debate using original survey data from two cross-sectional waves (2021 and 2023) covering more than 2700 respondents in Edo State, Nigeria. A substantial share of respondents reports a willingness to migrate via traffickers despite awareness of the risks of forced labor. A list experiment provides suggestive evidence of underreporting of trafficking approval, particularly among women, likely reflecting stigma surrounding sex work. We examine the determinants of trafficking approval through an aspirations-capabilities framework. Willingness to migrate via traffickers is highest among individuals with strong migration aspirations but limited capabilities. In contrast, exposure to anti-trafficking campaigns has little effect. Respondents are generally well-informed about the potential risks and returns associated with trafficking and do not exhibit cognitive biases such as motivated reasoning. Overall, our findings suggest that trafficking is not primarily driven by ignorance, but instead reflects a constrained choice shaped by limited legal migration options and structural barriers.

We hypothesize that polygyny acts as a significant push factor for migration in sub-Saharan Africa because it is associated with competition within polygynous families and on the marriage market, while also contributing to unfavorable economic and political outcomes at the societal level. Using cross-country data from 46 sub-Saharan African countries, we show that higher polygyny prevalence is associated with increased international emigration. We complement this macro-level evidence with original survey data from Senegal, the Gambia, and Nigeria. We show that polygyny is also associated with higher migration aspirations and observed migration of survey respondents’ siblings at the individual level. Respondents from polygynous families tend to report stronger economic motives for migration, while those concerned about the marriage market effects of polygyny—regardless of family background—are more likely to consider migrating for marriage. This highlights two distinct pathways—competition within polygynous families and on marriage markets—linking polygyny to migration.

This study investigates researcher variability in computational reproduction, an activity for which it is least expected. Eighty-five independent teams attempted numerical replication of results from an original study of policy preferences and immigration. Reproduction teams were randomly grouped into a ‘transparent group’ receiving original study and code or ‘opaque group’ receiving only a method and results description and no code. The transparent group mostly verified original results (95.7% same sign and p-value cutoff), while the opaque group had less success (89.3%). Second-decimal place exact numerical reproductions were less common (76.9 and 48.1%). Qualitative investigation of the workflows revealed many causes of error, including mistakes and procedural variations. When curating mistakes, we still find that only the transparent group was reliably successful. Our findings imply a need for transparency, but also more. Institutional checks and less subjective difficulty for researchers ‘doing reproduction’ would help, implying a need for better training. We also urge increased awareness of complexity in the research process and in ‘push button’ replications.

How do climate disasters shape migration? The existing evidence presents conflicting and inconclusive findings. To address this question, we theorise the cognitive processes guiding migration decisions in the wake of disasters. On the one hand, the link between climate disasters and migration aspirations may be driven by sudden-onset (e.g. heavy rains, storms and landslides) rather than gradual-onset events (e.g. droughts) because the devastating effect of the former may be easier to perceive. On the other hand, gradual climate disasters may be more influential because they can be perceived as more irreversible given their protracted nature. To test our hypotheses, we analyse original survey data from a representative sample of 5,700 individuals in Senegal and the Gambia. We show that individual perceptions of past climate disasters predict higher migration aspirations, a result robust to controlling for objective past climate conditions. On closer inspection, we show that only individuals with experience with gradual-onset events report higher migration aspirations, while experience with sudden-onset events has no comparable effect. Consistent with our regression analysis, results from an embedded survey experiment show that informational cues about future climate stress only impact the migration aspirations of individuals which have experienced gradual-onset weather events in the past.

How does the viewing of social media content produced by Senegalese migrants residing in Europe correlate with migration aspirations of people in Senegal? We answer this research question by interrogating original survey data from two regions in Senegal, Dakar and the Casamance, as well as original interview data of (potential) Senegalese migrants, repatriates, migration experts, and stakeholders. Using a mixed-methods approach that combines our qualitative interview and quantitative survey data, we provide robust evidence that viewing more social media content produced by compatriots in Europe coincides with stronger migration aspirations among respondents in Dakar and the Casamance. We also shed light on potential mechanisms. Here, our findings suggest that viewers of social media content by Senegalese migrants in Europe express higher admiration for migrants, consider the migration journey to Europe to be more viable and expect life in Europe to be especially rewarding. Our findings are in line with the cognitive migration model, which posits that migration aspirations are shaped by the potential migrants' mental time travel to an imagined future abroad. We argue that browsing social media content produced by Senegalese migrants residing in Europe creates particularly positive notions about migration and life in Europe, fueling migration aspirations by facilitating and making the cognitive migration of people in Dakar and the Casamance especially appealing.

How does anti-American terrorism in recipient countries respond to US military aid? Does aid protect United States interests abroad or does it have unintended consequences for US security? To answer these questions, we estimate the effect of US military aid on anti-American terrorism in recipient countries for a sample of 174 countries between 1968 and 2018. We find that higher levels of aid especially for military financing and education are associated with a higher likelihood of anti-American terrorism in aid-receiving countries. Examining potential transmission channels, we show that more US military aid correlates with lower military capacity and increases in corruption and exclusionary policies in recipient countries. Our findings are consistent with the argument that military aid aggravates local grievances, creating anti-American resentment and leading to anti-American terrorism. Indeed, we also provide tentative evidence that US military aid is associated with lower public opinion about the United States in recipient countries.

We examine the effect of rising temperatures on regional economic development, using annual sub-national data for over 1500 regions in 152 countries between 1990 and 2017. In a panel setting with region- and country-year fixed effects, we find no evidence of a homogeneous or heterogeneous effect of rising temperatures on economic development as measured by regional per capita income. Additionally, we find no non-linear relationship between temperature and economic development. We also employ a long-difference approach that is attuned to exploring the long-run relationship between rising temperatures and regional income. Results indicate that rising temperatures have a negative long-run impact on regional per capita income for a minority of regions located in countries with weak economic, legal and political institutions. Furthermore, these vulnerable regions experience a decline in long-term population and human capital development. The use of alternative regional per capita GDP data from 1950 onwards yields similar empirical results. Our findings suggest that negative economic effects of temperature increase with time, only becoming apparent in the long run for regions in already disadvantaged countries. Thus, country-specific conditions may moderate regional economic vulnerability to future temperature increases due to global climate change.

We leverage plausibly exogenous variation in regional exposure to corruption to provide causal estimates of the impact of local political corruption on terrorist activity for a sample of 175 countries between 1970 and 2018. We find that higher levels of corruption lead to more terrorism. This result is robust to a variety of empirical modifications, including various ways in which we probe the validity of our instrumental variables approach. We also show that corruption adversely affects the provision of public goods and undermines counter-terrorism capacity. Thus, our empirical findings are consistent with predictions from a game-theoretical representation of terrorism, according to which corruption makes terrorism relatively more attractive compared to peaceful contestation, while also decreasing the costs of organizing and carrying out terrorist attacks.

What is the causal impact of terrorism on immigration policy preferences? Under what circumstances and due to which psychological micro-mechanisms does this impact materialize? To answer these questions, we provide evidence from pre-registered and well-powered experiments for Germany and the United Kingdom. We find that anti-immigration responses to terrorism follow an emotional proximity rationale: terrorism leads to more restrictive migration policy preferences only among individuals with high levels of perceived insecurity, especially when terrorism occurs in their own country. Policy preferences are not affected by terrorism abroad or by information cues on the objectively low probability of being victimized.

How does terrorism affect child mortality? We use geo-coded data on terrorism and spatially disaggregated data on child mortality to study the relationship between both variables for 52 African countries between 2000 and 2017 at the 0.5 × 0.5° grid level. Our estimates suggest that moderate increases in terrorism are linked to several thousand additional annual deaths of children under the age of five. A panel event-study points to economic effects that are larger and compound over time. Interrogating our data, we show that the direct impact of terrorism tends to be very small. Instead, we theorize that terrorism causes child mortality primarily by triggering adverse behavioral responses by parents, medical workers, and policymakers. We provide tentative evidence in support of this argument.

We investigate the effect of Islamist terrorist activity on women's legal position in society, using data for 171 countries between 1970 and 2016. To identify causal effects, we exploit the prevalence of Islamist terrorism in neighboring countries as an exogenous source of variation, arguing that regional terrorism affects local terrorism through contagion effects. We show that increased activity by Islamist terrorist groups is linked to lower legal status of women. By contrast, we find that neither Islam per se nor other types of terrorism have comparable effects. This reinforces the notion that Islamist terrorism is singularly interested and effective in weakening women's rights. Our results are consistent with a rational-economic model of terrorism, where Islamist terrorists purposefully use violence to maximize political utility, while governments make concessions that constrain the role of women because the costs of compliance are lower than the harm from continued Islamist terrorism.

The aim of this paper is to review quantitative large-N studies that investigate the effects of climate change on migration flows. Recent meta-analyses have shown that most studies find that climate change influences migration flows. There are however also many studies that find no effects or show that effects are dependent on specific contexts. To better understand this complexity, we argue that we need to discuss in more detail how to measure climate change and migration, how these measurements relate to each other and how we can conceptualise the relationship between these two phenomena. After a presentation of current approaches to measuring climate change, international and internal migration and their strengths and weaknesses we discuss ways to overcome the limitations of existing analytical frameworks.

How does terrorism affect child mortality? We use geocoded data on terrorism and highly spatially disaggregated data on child mortality to study the relationship between both variables for 52 African countries between 2000 and 2017 at the 0.5x0.5 degree grid-cell level. A two-way fixed-effects approach indicates that higher levels of terrorist activity correlate with higher levels of child mortality risk. Our estimates suggest that moderate increases in the terrorism index are linked to several thousand additional deaths of children under the age of five per year. Employing instrumental-variable and panel event-study approaches, we also provide causal evidence that terrorism increases the risk of death for children under the age of five. Effect sizes associated with these causal estimates are several times larger than those from the more conservative two-way fixed-effects approach. Finally, interrogating our data, we show that the direct effects of terrorism (e.g., in terms of its lethality and destruction of public health infrastructure) tend to be very small. This, in turn, suggests that increases in child mortality primarily emerge through the behavioral response of economic agents (parents, doctors, medical staff, aid workers and policymakers) to terrorism. Indeed, we provide evidence that higher levels of terrorist activity unfavorably correlate with several proximate causes of child mortality.

Analyzing 118 countries between 1960 and 2016, we find that higher temperatures correlate with higher urbanization rates in the long run, where this relationship is much more pronounced than any short-term linkage. The long-run relationship between global warming and urbanization is also conditional upon country-specific conditions. This long-run association is especially relevant in poorer and more agriculture-dependent countries with an urban bias as well as in initially non-urban countries in hotter climate zones. We also provide suggestive evidence that warming contributes to losses in agricultural productivity and to pro-urban shifts in public goods provision and that the global warming-urbanization nexus is partly mediated through these channels. Consequently, we argue that the estimated long-run relationship between temperature and urbanization partly captures the potential impact of increasing temperatures on urbanization via a rural push (by impairing agriculture) and an urban pull (via an increased demand for public goods primarily supplied in cities).