Natural Experiments Research Articles

Call for papers: Generating stronger evidence to inform policy and practice: natural experiments on built environments, health behaviours and chronic diseases

Call for papers: Generating stronger evidence to inform policy and practice: natural experiments on built environments, health behaviours and chronic diseases

Causal inference in misinformation and conspiracy research

Psychological research has provided important insights into the processing of misinformation and conspiracy theories. Traditionally, this research has focused on randomized laboratory experiments and observational (non-experimental) studies seeking to establish causality via third-variable adjustment. However, laboratory experiments will always be constrained by feasibility and ethical considerations, and observational studies can often lead to unjustified causal conclusions or confused analysis goals. We argue that research in this field could therefore benefit from clearer thinking about causality and an expanded methodological toolset that includes natural experiments. Using both real and hypothetical examples, we offer an accessible introduction to the counterfactual framework of causality and highlight the potential of instrumental variable analysis, regression discontinuity design, difference-in-differences, and synthetic control for drawing causal inferences. We hope that such an approach to causality will contribute to greater integration amongst the various misinformation- and conspiracy- adjacent disciplines, thereby leading to more complete theories and better applied interventions.

Numerical study of the interaction of a shock wave with a layer of particles using the Baer–Nunziato model

The work is devoted to the application of the Baer–Nunziato model to study shock wave processes in particle beds. The numerical algorithm is based on an HLLC-like solver and takes into account the processes of establishing equilibrium at the interface, taking into account the effect of particle compaction. The problem statement corresponds to the full-scale experiment of B.C. Fan et al. As part of the work, qualitative and quantitative agreement was obtained with the results of natural experiments and calculations of other authors, and an explanation was proposed for the experimentally observed phenomena.

Growth data of outlying plantations allows benchmarking the tolerance to climate extremes and drought stress in the European larch.

Plantations located outside the species distribution area represent natural experiments to assess tree tolerance to climate variability. Climate change amplifies warming-related drought stress but also leads to more climate extremes. We studied plantations of the European larch (Larix decidua), a conifer native to central and eastern Europe, in northern Spain. We used climate, drought and tree-ring data from four larch plantations including wet (Valgañón, site V; Santurde, site S), intermediate (Ribavellosa, site R) and dry (Santa Marina, site M) sites. We aimed to benchmark the larch tolerance to climate and drought stress by analysing the relationships between radial growth increment (hereafter growth), climate data (temperature, precipitation, radiation) and a drought index. Basal area increment (BAI) was the lowest in the driest site M (5.2 cm2 yr-1; period 1988-2022), followed by site R (7.5 cm2 yr-1), with the youngest and oldest and trees being planted in M (35 years) and R (150 years) sites. BAI peaked in the wettest sites (V; 10.4 cm2 yr-1; S, 10.8 cm2 yr-1). We detected a sharp BAI reduction (30% of the regional mean) in 2001 when springto-summer conditions were very dry. In the wettest V and S sites, larch growth positively responded to current March and June-July radiation, but negatively to March precipitation. In the R site, high April precipitation enhanced growth. In the driest M site, warm conditions in the late prior winter and current spring improved growth, but warm-sunny conditions in July and dry-sunny conditions in August reduced it. Larch growth positively responded to spring-summer wet conditions considering short (1-6 months) and long (9-24 months) time scales in dry (site M) and wet-intermediate (sites S and R) sites, respectively. Larch growth is vulnerable to drought stress in dry slow-growing plantations, but also to extreme spring wet-cloudy events followed by dry-hot conditions in wet fast-growing plantations.

A Demand Curve for Disaster Recovery Loans

We estimate and trace a credit demand curve for households that recently experienced damage to their homes from a natural disaster. Our administrative data include over one million applicants to a federal recovery loan program for households. We estimate extensive‐margin demand over a large range of interest rates. Our identification strategy exploits 24 natural experiments, leveraging exogenous, time‐based variation in the program's offered interest rate. Interest rates meaningfully affect consumer demand throughout the distribution of rates. On average, a 1 percentage point increase in the interest rate reduces loan take‐up by 26%. We find a large impact of applicants' credit quality on demand and evidence of monthly payment targeting. Using our estimated demand curve and information on program costs, we find that the program generates an average social surplus of $2900 per borrower.

Using Natural Experiments in Public Enterprise Management

Using Natural Experiments in Public Enterprise Management

The effect of obtaining EU citizenship in former transition economies on remittance flows

AbstractWe estimate the effect of the granting of European Union (EU) citizenship rights on the flow of remittances from Italy. We use the EU enlargements of 2007 and 2013 as natural experiments. The results show a negative impact on remittance flows. The effect of the 2007 EU enlargement shows how Romanian and Bulgarian citizens reduced the average annual amount of remittances by 1400 Euros per year per migrant. In the case of the 2013 EU enlargement, we find a smaller decrease of about 50 Euros per year per Croat. These results are consistent after a series of robustness checks. We analyse this decline in depth to the extent that remittances are an important source of monetary flows in transition economies. We find that both the change in the taxonomy of immigrants from the new Member States and the improvement of economic conditions in the country of origin after the EU accession provide suggestive evidence on plausible mechanisms behind our results.

How much schizophrenia do famines cause?

Since the 1970s, famines have been widely invoked as natural experiments in research into the long-term impact of foetal exposure to nutritional shocks. That research has produced compelling evidence for a robust link between foetal exposure and the odds of developing schizophrenia. However, the implications of that research for the human cost of famines in the longer run have not been investigated. We address the connection between foetal origins and schizophrenia with that question in mind. The impact turns out to be very modest—much less than one per cent of the associated famine death tolls—across a selection of case studies.

USE OF AQUEOUS EMULSIONS OF WASTE MOTOR OILS AS HIGH-EFFICIENCY FUEL

This work presents the methodology of using wasted lubricants as a highly efficient fuel as water-fuel emulsions, which containing up to 70% water. They burning in burners under conditions of action high-frequency electrical discharges. It has been shown that the viscosity of a water-oil emulsion with a high water part (more than 50%) outweighs the viscosity of pure oil. With a low water part (10-20%), the emulsion is the most stable. With more water, the semi-delamination time decreases. Therefore, it is necessary to spray the emulsion near the site of the making. The results of natural experiments and prospects of the proposed methodology are given. Combustion of a water-in-oil emulsion with a volume content of 50-70% water is possible in the presence of a discharge of high-frequency signals. Independent combustion of the emulsion without the support of a small diesel fuel torch is possible with sufficient heating of the combustion chamber. To implement combustion, the burner for liquid fuels was modernized by adding a pre-chamber between the burner and the nozzle or boiler. To organize effective spraying of water-oil emulsion with a large amount of water (up to 70%), it is necessary to ensure sufficient heating of the emulsion in the pipelines. First, this reduces its viscosity, making it easier to pump the emulsion through the supply systems of the spraying device. Otherwise, it is necessary to serve under a pressure, so that the water at a high temperature (above 100 ° C) is remained liquid. When leaving the nozzle under pressure, the water “boils” (“micro-bump” drops of emulsion), which further disperses the burning liquid. The peculiarity of this burner is the action of a high-frequency streamer in the area of spraying emulsion droplets inside the forechamber. The use of water-fuel emulsions allows to reduce emissions of nitrogen oxides and carbon monoxide, reduce its fire and explosion hazard during transportation and storage. Effectiveness assessment of this complex showed that energy expenditures can reach percents of levels compared to full heat release.Thus, the possibility of using such water-oil emulsions as alternative fuels is shown. Keywords: water-oil emulsion, high-frequency electric discharge, combustion, torch.

Natural Experiments as a Study Method in Spinal Trauma Surgery: A Systematic Review.

Systematic review. To determine if the natural experiment design is a useful research methodology concept in spinal trauma care, and to determine if this methodology can be a viable alternative when randomized controlled trials are either infeasible or unethical. A Medline, Embase and Cochrane database search was performed between 2004 and 2023 for studies comparing different treatment modalities of spinal trauma. All observational studies with a natural experiment design comparing different treatment modalities of spinal trauma were included. Data extraction and quality assessment with the MINORS criteria was performed. Four studies with a natural experiment design regarding patients with traumatic spinal fractures were included. All studies were retrospective, one study collected follow-up data prospectively. Three studies compared different operative treatment modalities, whereas one study compared different antibiotic treatment strategies. Two studies compared preferred treatment modalities between expertise centers, one study between departments (neuro- and orthopedic surgery) and one amongst surgeons. For the included retrospective studies, MINORS scores (maximum score 18) were high ranging from 12-17 and with a mean (SD) of 14.6 (1.63). Since 2004 only four studies using a natural experiment design have been conducted in spinal trauma. In the included studies, comparability of patient groups was high emphasizing the potential of natural experiments in spinal trauma research. Natural experiments design should be considered more frequently in future research in spinal trauma as they may help to address difficult clinical problems when RCT's are infeasible or unethical.

An Evidence-based Meta-analysis on the Outcomes of Teacher Education under the Concept of Outcome-Based Education

Currently, there is limited empirical research on the educational outcomes of Outcome-based Education (OBE) theory, making it challenging to draw clear inferences based on logical deductions in real-world contexts. Taking a certain university in Wuhan city as an example, this study conducted 50 regression analyses on the curriculum as the research subject, employing both Meta-analysis and Meta-regression analysis as natural experiments. The findings reveal that the implementation of OBE reforms significantly enhances the educational outcomes of teachers, although the impact shows substantial heterogeneity. Firstly, the classroom learning environment has a significant positive impact on educational outcomes. Secondly, the study found that implementing OBE reforms has significantly positive effects on professional courses and platform courses, while showing insignificant effects on general education and elective courses. Thirdly, the effects of OBE reforms are more pronounced for students in science and engineering as well as business and management disciplines, whereas insignificant for students in humanities and arts disciplines. Based on these findings, the following policy recommendations are proposed: there should be a firm commitment to the implementation of OBE reforms, and it is advisable to expand the scope of OBE reforms to a larger scale. Furthermore, OBE reforms can be selectively implemented across all courses, and efforts should be made to ensure clarity of objectives when implementing OBE reforms in disciplines related to humanities and arts.

Prioritizing a research agenda on built environments and physical activity: a twin panel Delphi consensus process with researchers and knowledge users

BackgroundThe growth of urban dwelling populations globally has led to rapid increases of research and policy initiatives addressing associations between the built environment and physical activity (PA). Given this rapid proliferation, it is important to identify priority areas and research questions for moving the field forward. The objective of this study was to identify and compare research priorities on the built environment and PA among researchers and knowledge users (e.g., policy makers, practitioners).MethodsBetween September 2022 and April 2023, a three-round, modified Delphi survey was conducted among two independent panels of international researchers (n = 38) and knowledge users (n = 23) to identify similarities and differences in perceived research priorities on the built environment and PA and generate twin ‘top 10’ lists of the most important research needs.ResultsFrom a broad range of self-identified issues, both panels ranked in common the most pressing research priorities including stronger study designs such as natural experiments, research that examines inequalities and inequities, establishing the cost effectiveness of interventions, safety and injuries related to engagement in active transportation (AT), and considerations for climate change and climate adaptation. Additional priorities identified by researchers included: implementation science, research that incorporates Indigenous perspectives, land-use policies, built environments that support active aging, and participatory research. Additional priorities identified by knowledge users included: built environments and PA among people living with disabilities and a need for national data on trip chaining, multi-modal travel, and non-work or school-related AT.ConclusionsFive common research priorities between the two groups emerged, including (1) to better understand causality, (2) interactions with the natural environment, (3) economic evaluations, (4) social disparities, and (5) preventable AT-related injuries. The findings may help set directions for future research, interdisciplinary and intersectoral collaborations, and funding opportunities.

Virulence of Dothistroma septosporum and D. pini on Pinus nigra and P. mugo under conditions of natural infection

AbstractDothistroma needle blight (DNB) is a severe needle disease of pines worldwide, caused by two closely related species, Dothistroma septosporum and D. pini. The two fungal species are similar not only in their morphological characteristics, but also cause very similar symptoms in their hosts, and have a similar ecology. The aim of this study was to compare the virulence of the two Dothistroma species in natural infection experiments on 2-year-old seedlings of two DNB susceptible pine species, Pinus nigra and P. mugo, in two seedling stands for each pathogen species. The virulence of the pathogens and presence of symptoms (symptomatic needles, red bands and acervuli) were assessed after 2 years of exposure to inoculum. The incidence of seedlings with DNB symptoms was 65% and 76% for P. nigra and P. mugo, respectively. No difference was found between D. septosporum and D. pini in any of the three DNB symptoms evaluated on seedlings of P. mugo. However, symptoms of disease differed between the two Dothistroma species on P. nigra. Variables that reflect the intensity of disease development, the number of red bands and acervuli per needle, showed a difference in virulence between D. septosporum and D. pini, but only in the case of the host species P. nigra. The results suggest that the virulence of the two Dothistroma species could be affected by host pine species and that there are differences in the susceptibility of individual pine species to D. septosporum and D. pini. Further factors could affect the virulence of these pathogens, including isolate origin, climatic or environmental factors.

Call for papers: Generating stronger evidence to inform policy and practice: natural experiments on built environments, health behaviours and chronic diseases

Call for papers: Generating stronger evidence to inform policy and practice: natural experiments on built environments, health behaviours and chronic diseases

Justifying calculations of snow load distribution on snow retaining structures in avalanche protection system

Snow load estimation is one of the most important tasks in designing snow-retaining structures for avalanche protection of railways and motorways in mountainous areas. The situation is complicated by the fact that avalanches are subdivided, depending on the consistency of snow, into dry, wet and damp avalanches. This paper analyses the existing foreign and domestic snow load calculation methods, based on which was concluded that there is no dependence of the load value on the physical and mechanical parameters distribution of the snow cover in all the considered methods of calculation. Moreover, none of these methods makes it possible to estimate the snow pressure distribution on a snow-retaining structure by its depth. The article proposes an alternative way of calculating the snow layer pressure using the developed discrete model for calculating the static snow pressure distribution on a barrier by its depth. The discrete model peculiarity is to take into account the change of physical and mechanical characteristics of snow — density, specific adhesion and angle of internal friction, by layers of natural deposit. Discrete model verification was performed by comparing the calculated and experimental data obtained as a result of both natural and laboratory experiments. The experiments were conducted in laboratory conditions on a special model, using a material with stable physical and mechanical characteristics that do not change during the course of the experiment. Also, for verification, the field experiment results on determining the naturally deposited snow pressure on an obstacle, taken from the open press, were used.

Causal attribution of agricultural expansion in a small island system using approximate Bayesian computation

The extent and arrangement of land cover types on our planet directly affects biodiversity, carbon storage, water quality, and many other critical social and ecological conditions at virtually all scales. Given the fundamental importance of land cover, a key mandate for land system scientists is to describe the mechanisms by which pertinent cover types spread and shrink. Identifying causal drivers of change is challenging however, because land systems, such as small-scale agricultural communities, do not lend themselves well to controlled experimentation for logistical and ethical reasons. Even natural experiments in these systems can produce only limited causal inference as they often contain unobserved confounding drivers of land cover change and complex feedbacks between drivers and outcomes. Land system scientists commonly grapple with this complexity by using computer simulations to explicitly delineate hypothesized causal pathways that could have resulted in observed land cover change. Yet, land system science lacks a systematic method for comparing multiple hypothesized pathways and quantifying the probability that a given simulated causal process was in fact responsible for the patterns observed. Here we use a case study of agricultural expansion in Pemba, Tanzania to demonstrate how approximate Bayesian computation (ABC) provides a straightforward solution to this methodological gap. Specifically, we pair an individual-based simulation of land cover change in Pemba with ABC to probabilistically estimate the likelihood that observed deforestation from 2018 to 2021 was driven by soil degradation rather than external market forces. Using this approach, we can show not only how well a specific hypothesized mechanism fits with empirical data on land cover change, but we can also quantify the range of other mechanisms that could have reasonably produced the same outcome (i.e. equifinality). While ABC was developed for use in population genetics, we argue that it is particularly promising as a tool for causal inference for land system science given the wealth of data available in the satellite record. Thus, this paper demonstrates a robust process for identifying the emergent landscape-level signatures of complex social-ecological mechanisms.

Study and Application of Estimation Method for Environmental Background Pollution Fluxes into the River in Source Areas

The background values of pollutants are becoming increasingly prominent in evaluating water quality and management, and their load and output characteristics are of great significance to the study of changes in the background values. Thus, this paper studies the estimation method for background pollutant fluxes into a river in a forested river source in northeastern China with deficient data or without data. Based on the results of a soak experiment and leaching experiment, as well as natural rainfall runoff experiments, the conversion relationship of the pollutant concentration in the medium was established, the transformation relationship of the pollutant concentration in the medium was established, its load into the river in a small watershed was estimated, and the estimation method was verified according to the measurements (average relative error: 20.5%). Then, the background pollutant loading into the river was calculated on a large scale by improving the pollutant output coefficient model and the universal soil loss equation (average relative error: 18.7%, 24.7%). The results show that the method mentioned above can better reflect the background pollutant loading into the river. This study provides an effective strategy to estimate the background pollutant loading into rivers in areas without data or with missing data, and also provides a theoretical basis for the study of zoning and the formulation of a water environment evaluation system based on background values.

On the stability of preferences: Experimental evidence from two disasters

We investigate the impacts of two disasters in Japan and the Philippines on preferences using the convex time budget experiments and multiple price list experiments with monetary rewards. By exploiting natural experiments which are combined with lab-in-the-field experiments, we aim to investigate whether and how long preferences are affected by extreme events. We find evidence supporting preference instability caused by exposure to natural hazards: in both our study sites, disaster exposure seems to make individuals more present-biased even though they differ in socioeconomic conditions and disaster types. The estimated impacts are persistent over the short and long time intervals in both disaster-affected areas and are robust to the method of measuring preferences.

Call for papers: Generating stronger evidence to inform policy and practice: natural experiments on built environments, health behaviours and chronic diseases

Call for papers: Generating stronger evidence to inform policy and practice: natural experiments on built environments, health behaviours and chronic diseases

Using Natural Experiments to Uncover Effects of Anti-Refugee Riots on Attitudes of Refugees

While previous research has focused on terrorist attacks and natives’ attitudes towards immigration, we examine the effect of anti-refugee attacks on refugees’ attitude towards the host country. We use survey data from the 33rd wave of the German Socio-Economic Panel as the fieldwork period overlapped with the infamous anti-refugee riots in Bautzen and as the survey includes a refugee sample. Making use of this natural experiment, we find significant and negative short-term effects of the riots on respondents’ perception of Germany, as well as low geographic variation. Such natural experiments in the form of unexpected events during survey design offer social scientists the possibilities to identify causal effects from observational survey data as they split respondents into a control and treatment group. Given the vast amount of (cross-)national survey data, often including specific subsamples, our study demonstrates the great potential of natural experiments for sociological research on minority groups in society.