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11. Simultaneous estimation and modeling of nonlinear, non- Gaussian state-space systems

Author:
Josiah Steckenrider and Furukawa Tomonari
Publication Date:
07-2021
Content Type:
Research Paper
Institution:
Department of Social Sciences at West Point, United States Military Academy
Abstract:
This paper presents a framework for simultaneous estimation and modeling of nonlinear, non-Gaussian state-space systems. In the proposed approach, uncertainty in motion model parameters is incorporated to avoid overconfidence in state prediction and better account for modeling inaccuracies. The additional original contribution of a model correction stage improves nonlinear model parameter estimates in order to enhance the accuracy of state estimation. The presented nonlinear/non-Gaussian Simultaneous Estimation And Modeling (SEAM) approach was compared with contemporary estimation techniques using a Monte-Carlo simulation study. This study showed that the proposed method successfully reduces estimation error relative to existing approaches even when substantial model parameter uncertainty and multi-modal sensor noise are present. The framework has potential use in a wide range of applications where state-space estimation is employed, including robotics, signal processing, and controls.
Topic:
Science and Technology, Space, Artificial Intelligence, and Models
Political Geography:
Global Focus

12. Modeling and Simulation as a Bridge to Advance Practical and Theoretical Insights About Forced Migration Studies

Author:
Erika Frydenlund
Publication Date:
11-2021
Content Type:
Journal Article
Journal:
Journal on Migration and Human Security
Institution:
Center for Migration Studies of New York
Abstract:
Modeling and Simulation (M&S) is a relatively unused research approach in forced migration studies. In most of its application areas, M&S is applied in several broad thematic policy-oriented topics: predicting human movement, humanitarian logistics, communicable diseases, healthcare, policing, and economics. More recently, there has been increased use of M&S in predicting human movement and health impacts resulting from climate change. Computer modeling has benefits for both policy and theoretical advancements in the field. M&S is often associated as a predictive tool that appeals to policymakers and planners. But M&S has many other significant benefits. For policymakers and planners, M&S provides a simulated environment to explore “what-if” scenarios. These scenarios can be adjusted to reflect different assumptions and conditions in the field. M&S can provide a means for translating interpretivist research findings—themselves rich in descriptions of actors, relationships, and dynamics—into visual artifacts that can communicate results to policymakers. It also can help to test the assumptions of theoretical findings, explore generalizability to other cases and conditions, and inform future data collection efforts. On the other hand, because models can take a long time to construct and test, they cannot provide rapid insights about evolving situations to inform decision-making at the onset of a new emergency. Data dashboards, the staple of modern humanitarian operations, are better for identifying emergent needs and tracking efforts. However, modeling what we know from one situation allows us to use those insights in systematic and strategic ways to improve operations for the future. M&S can also provide researchers with an additional tool that allows improved integration of multiple data types and sources. These data, assumptions, and theoretical constructs can be linked together in a complex, nonlinear, dynamic system that can then be set in motion to see if the simulated world reveals phenomena that are witnessed in the real world. But interdisciplinary communication and collaboration is hard and finding modelers who value interpretivist research can be even harder. M&S is not a silver bullet but provides a unique approach that incorporates dynamics and is becoming increasingly accessible to policymakers, practitioners, and academics, including those without computer programing experience. For policy, it is important to invest the time and resources to develop simulation models—from simple to complex—that help when planning for the evolution of events, or for the next event. Models of current refugee situations should inform where to concentrate efforts to advance durable solutions and how to plan for potential scenarios of return to countries of origin. Policymakers must recognize the long-term value of modeling what we know now to use later. Researchers of migration should become familiar with M&S paradigms so they can become part of the model design, development, and testing phases—at least part of the conversation. Better integration of migration scholars in design and development has the potential to strengthen models for policymaking, but perhaps more importantly, to strengthen the field by serving as an extra tool for testing theories, assumptions, and generalizability of findings to other locations and situations.
Topic:
Migration, Models, Forced Migration, and Simulation
Political Geography:
Global Focus

13. Civil War Violence and Refugee Outflows

Author:
Andrew Shaver
Publication Date:
04-2021
Content Type:
Working Paper
Institution:
Empirical Studies of Conflict Project (ESOC)
Abstract:
Conflict forces millions of individuals from their homes each year. Using a simple structural model and new refugee data, we produce the first set of estimates relating outflows to annual conflict magnitudes. The theory underlying the structural model implies that standard panel data approaches will underestimate the impact of conflict violence, by differencing out the effect of prior and expected levels of violence on the decisions to flee. We estimate that whereas a shock that doubles conflict deaths in one year increases outflows in that year by 40% on average, doubling conflict deaths in all years increases annual outflows by 100%. We further estimate an average of 30 refugees per conflict death (median 18), with higher rates for conflicts closer to an OECD country and possibly for ethnic wars and in lower income countries. The analysis illustrates a broader methodological point: It can be hazardous to try to identify a causal effect using shocks to a presumed causal factor if the outcome variable is the result of decisions based not only on shocks but also on levels.
Topic:
Political Violence, Civil War, Refugee Issues, Refugees, Refugee Crisis, Data, Armed Conflict, and Models
Political Geography:
Global Focus

14. GARCH Analyses of Risk and Uncertainty in the Theories of the Interest Rate of Keynes and Kalecki

Author:
Hubert Gabrisch
Publication Date:
01-2021
Content Type:
Working Paper
Institution:
The Vienna Institute for International Economic Studies (WIIW)
Abstract:
This study attempts to identify uncertainty in the long-term rate of interest based on the controversial interest rate theories of Keynes and Kalecki. While Keynes stated that the future of the rate of interest is uncertain because it is numerically incalculable, Kalecki was convinced that it could be predicted. The theories are empirically tested using a reduced-form GARCH-in-mean model assigned to six globally leading financial markets. The obtained results support Keynes’s theory – the long-term rate of interest is a nonergodic financial phenomenon. Analyses of the relation between the interest rate and macroeconomic variables without interest uncertainty are thus seriously incomplete.
Topic:
Economics, International Political Economy, Economic Theory, Interest Rates, Macroeconomics, Keynes, Models, and Michał Kalecki
Political Geography:
Global Focus

15. Marching to Good Laws: The Impact of War, Politics, and International Credit on Reforms in Ukraine

Author:
Artem Kochnev
Publication Date:
01-2021
Content Type:
Working Paper
Institution:
The Vienna Institute for International Economic Studies (WIIW)
Abstract:
The paper investigates determinants of investments in state capacity and institutional change in contemporary Ukraine. After formulating a simple sequential two-stage model of investments in state capacity, the paper estimates autoregressive distributed lag and vector autoregressive models to verify its predictions. The paper finds little evidence for the impact of conflict intensity and access to international credit on the pace of reform progress. It finds a statistically significant effect for the intensity of political competition and changes of real wages, albeit these results are sensitive to robustness checks.
Topic:
Economics, International Political Economy, War, Labor Issues, Credit, International Business, State Capitalism, and Models
Political Geography:
Ukraine

16. Impacts of COVID-19 on the Energy Demand Situation of East Asia Summit Countries

Author:
Shigeru Kimura, Ikarii Ryohei, and Endo Seiya
Publication Date:
07-2021
Content Type:
Research Paper
Institution:
Economic Research Institute for ASEAN and East Asia (ERIA)
Abstract:
The coronavirus disease (COVID-19) pandemic has brought us a ‘New Normal’ life style and the lockdown has severely harmed economic growth, with many countries estimated to record negative economic growth in 2020. Due to the high correlation between energy demand and economic growth, energy demand is also affected. Against this background, ERIA analyses how energy demand has decreased as a result of the COVID-19 pandemic using East Asia Summit (EAS) energy outlook models that are regularly updated by ERIA and apply an econometric approach. The outlook models cover the Association of Southeast Asian Nations (ASEAN) 10 countries plus seven countries – Australia, China, India, Japan, Republic of Korea, New Zealand, and the United States. According to gross domestic product (GDP) growth estimates for EAS countries in 2020, only three countries – China, Lao PDR, and Viet Nam – show positive growth, though less than 2%, and the others show negative growth. Total Final Energy Consumption (TFEC) of the EAS countries fell in 2020, but it is expected to rebound in 2021 and projected to return to the originally forecast trend of energy demand up to 2050. Once official energy statistics become available, a comparison between model results and actual statistics will be made to understand how the energy outlook models trace the impact of the pandemic on energy demand.
Topic:
Energy Policy, Pandemic, COVID-19, and Models
Political Geography:
East Asia and Asia

17. New Directions in Macroeconomics

Author:
Gillian Brunet
Publication Date:
07-2021
Content Type:
Policy Brief
Institution:
Economics for Inclusive Prosperity (EfIP)
Abstract:
Without being overly prescriptive, macro research must meet two standards to keep the field moving in a productive direction: models must be tested empirically and researchers must think carefully about how underlying assumptions restrict the set of questions that can be answered with a given model. Models move knowledge forward through rigorous empirical testing. Matching moments in model calibration is not enough—nor should it be considered true empirics. When economics is done well, theory and empirics are complements: empirical research disciplines models and theory disciplines empirical research. In recent decades, macro research has tilted very heavily towards theory, forgoing the feedback generated by rigorous empirical testing and, as a consequence, dramatically reducing the ratio of insight to effort. Macro as a field must value empirical contributions to flourish fully. There has been significant progress in the last decade, but the balance still tilts heavily towards theory. Macroeconomists must stop dismissing empirical contributions as trivial for macro theory to reach its potential. It’s not an accident that many of today’s best macroeconomists stand out for their work in both theory and empirics: empirical work disciplines their theoretical research. Over the past 40-50 years, research in short-run macroeconomics has focused on the goal of creating unified, internally consistent models of the macroeconomy. While this is a worthy goal, it has perhaps become too dominant—and imposes hidden costs on research. The emphasis on developing a central baseline model to which idiosyncratic features are added for addressing a specific problem discourages many researchers from considering the suitability of the underlying model to the specific question being asked. As economists we are taught that every model is a simplification, so that the relevant question is not whether a model is good or bad but whether it is good or bad for answering a specific question. Yet choosing a single baseline model of the macroeconomy tends to obscure the closeness of the relationship between the model and the question it is used to answer. Often macroeconomists think carefully about the relationship between their question and the idiosyncratic features they add to the baseline model, but many of the assumptions underlying the baseline model become invisible and thus unquestioned. This is understandable given the complexity of modern macro models, but it has high costs. More careful consideration of the assumptions underlying baseline models and their appropriateness to individual research questions can help move the field forward.
Topic:
Economics, Political Economy, Macroeconomics, and Models
Political Geography:
United States

18. Love of Variety and Gains from Trade

Author:
Christophe Gouel and Sébastien Jean
Publication Date:
12-2021
Content Type:
Working Paper
Institution:
Centre d'Etudes Prospectives et d'Informations Internationales (CEPII)
Abstract:
This paper shows how gains from trade are conditioned by love of variety, defined as the extent to which an additional product variety generates benefits in either final or intermediate consumption. We develop a multi-country, multisector gravity trade model where love of variety is parameterized separately from product substitutability using a generalized CES demand function, and show analytically how gains from trade depend on love of variety through different channels that we identify and interpret. In this context, except for very specific parameterizations, gains from trade differ between a heterogeneous- and a homogeneous-firm model. Counterfactual simulations based on a calibrated version of this model show that, all other things being equal, the assessed gains from trade commonly vary by a proportion of one to three depending on the value of the love-of-variety elasticity, in a way that differs significantly across countries. Trade war simulations also point to the strong sensitivity of the assessed impacts. We conclude that love of variety is a key determinant of the gains from trade, an aspect that has so far been overlooked for the sake of convenience in the modeling framework and due to lack of empirical estimates.
Topic:
International Cooperation, International Trade and Finance, Trade Wars, and Models
Political Geography:
Global Focus

19. Poor Substitutes? Counterfactual methods in IO and Trade compared

Author:
Keith Head and Thierry Mayer
Publication Date:
12-2021
Content Type:
Working Paper
Institution:
Centre d'Etudes Prospectives et d'Informations Internationales (CEPII)
Abstract:
Constant elasticity of substitution (CES) demand for monopolistically competitive firm-varieties is a standard tool for models in international trade and macroeconomics. Inter-variety substitution in this model follows a simple share proportionality rule. In contrast, the standard toolkit in industrial organization (IO) estimates a demand system in which cross-elasticities depend on similarity in observable attributes. The gain in realism from the IO approach comes at the expense of requiring richer data and greater computational challenges. This paper uses the dataset of Berry et al. 1995, who established the modern IO method, to simulate counterfactual trade policy experiments. We use the CES model as an approximation of the more complex underlying demand system and market structure. Although the CES model omits key elements of the data generating process, the errors are offsetting, leading to reasonably accurate counterfactual predictions. For aggregate outcomes, it turns out that incorporating non-unitary pass-through matters more than fixing over-simplified substitution patterns. We do so by extending the commonly used methods of Exact Hat Algebra and tariff elasticity estimation to take into account oligopoly.
Topic:
Economics, Business, Monopoly, Trade, and Models
Political Geography:
Global Focus

20. Scenarios for an impact assessment of global bioeconomy strategies: results from a co-design process

Author:
Ruth Delzeit, Tobias Heimann, Franziska Schunemann, and Mareike Soder
Publication Date:
07-2021
Content Type:
Working Paper
Institution:
Kiel Institute for the World Economy (IfW)
Abstract:
The replacement of fossil resources with renewable biomass in a bioeconomy is seen as a major contribution to climate change mitigation. This transformation will affect all members of society, making it crucial to consider the views of different stakeholders to ensure a socially acceptable transition towards a sustainable bioeconomy. To explore potential outcomes of bioeconomy strategies assuming different future pathways, a scenario analysis is a tool to inform decision-makers about policy impacts and trade-offs. The inter- and transdisciplinary research project “BioNex – The future of the biomass nexus” is the first project to develop bioeconomy scenarios together with stakeholders from politics, industry, and civil society in an iterative co-design process. As a result, three storylines describing diverging potential global futures are developed and quantified: Towards sustainability, business as usual, and towards resource depletion. The futures are driven by different assumptions on climate policy, cropland expansion, productivity growth in agriculture, prices of fossil energy, and consumption behaviour. Additionally, in the co-design process, three bioeconomy policies are developed: policy as usual, stronger development of the bioeconomy, and no policies. Besides presenting the results of the stakeholder workshops, this paper evaluates the strengths and shortcomings of a stakeholder approach in terms of policy-oriented research. According to the experience made within this study, it provides valuable insights for researchers and funding authorities they can use to optimise the employment of stakeholder-based research approaches.
Topic:
International Cooperation, Economy, Biology, and Models
Political Geography:
Global Focus