Gravity Model Research Articles

Quantifying the impact of trade liberalization on Lao imports (evidence from product-level data)

In pursuing economic development after market-oriented reforms, Lao PDR has actively liberalized imports through engagement in regional and multilateral trade agreements. However, a substantial research gap exists in assessing the impact of this liberalization, especially in terms of ex-post empirical studies, which are essential for nuanced policy evaluation. This study aims to thoroughly quantify the impact of tariff liberalization on Lao imports, specifically examining how the elimination of tariffs under regional trade and multilateral trade schemes affects Lao imports. In this study, a balanced gravity panel dataset at a product level from 2013 to 2022 was constructed using data from the Lao Official Import Management Database for a standard gravity model analysis. Results of this analysis reveal that tariff liberalization has significantly boosted Lao imports with an elasticity of -0.327. Counterfactual analysis strengthens this finding, indicating an approximate 6.7% increase in the average value of imports from 2018 to 2022.

Chorological abductive inferring: case studies of tracing spatial dissemination of COVID-19

Abstract COVID-19 did not disappear in the third year (2022) of the global pandemic. On the contrary, the number of infected people several times exceeded the highs of previous years, but the greater morbidity was not accompanied by a relatively comparable number of deaths. Some studies showed that the SARS-CoV-2 virus impact, e.g. in CEE EU countries, characterizes the seasonal intensity as temperatures fall or rise in relative humidity. All researchers agree that the number of COVID-19-infected people is only an estimate based on the volume of tests performed and that the true numbers are usually much higher. The implementation of spatial interaction modeling could potentially aid in the control of the COVID-19 pandemic due to the inherently spatial nature of its diffusion. The gravity models used in this investigation to simulate the regional spread of the COVID-19 epidemic are based methodologically on previous empirical studies. The proposed methodology uses techniques for modeling spatial interactions due to the epidemics described above, which are a direct result of the number of contacts between individuals. The COVID-19 pandemic can be studied regionally using spatial diffusion methods as well as population potential models (spatial interaction models) and visualized using geographic information system software. Empirical verification and geovisualizations are based on available recent population and pandemic statistics that are possible to acquire from national health services. Methodologically, this type of modeling and simulation aimed at reconstructing a factual situation can be defined as abductive chorological inferring.

Analysis of Interregional Trade for Russian Far Eastern Regions Based on Gravity Models

Analysis of Interregional Trade for Russian Far Eastern Regions Based on Gravity Models

The semi-classical saddles in three-dimensional gravity via holography and mini-superspace approach

We determine the complex geometries dual to the semi-classical saddles in three-dimensional gravity with positive or negative cosmological constant. We examine the semi-classical saddles in Liouville field theory and interpret them in terms of gravity theory. For this, we describe the gravity theory by Chern-Simons theory and classify the possible saddles based on the homotopy group argument. We further realize the semi-classical saddles using the mini-superspace model of quantum gravity and explicitly determine the integral contour. In the case of positive cosmological constant, we recovered the geometry used for no-boundary proposal of Hartle and Hawking. In the case of negative cosmological constant, the geometry can be identified with Euclidean anti-de Sitter space attached with imaginary radius spheres. The geometry should be unphysical and several arguments on this issue are provided. Partial results were already presented in our earlier letter, and more detailed derivations and explanations on the results are given along with additional results. In particular, we reproduce the classical Liouville action from the Chern-Simons formulation of dual gravity theory.

Investigating subsurface structural lineaments of the northwest Ethiopian plateau using gravity data

This study provides advanced knowledge of the subsurface structural characteristics of the northwest Ethiopian plateau. With its complex geologic structure, the Northwest Ethiopian plateau is being studied for density boundary mapping using geophysical methods. However, its application to the mapping of geological structures such as faults and contacts which appear as lineaments in gravity data has not been studied so far. Thus, the goal of this research is to increase our understanding of the subsurface structural lineaments and their depth beneath the Ethiopian plateau in the northwest using global gravity model GGMplus2013. These subsurface structural lineaments and their depths were investigated using the LTHG, EHGA, and tilt depth techniques. The results indicate that the main subsurface structural lineaments identified in the study region are dipping between 3.2 and 8 km and are developing in the NE-SW, N–S, E-W, and NW-SE orientations.

Ensuring China's food security in a geographical shift of its grain production: Driving factors, threats, and solutions

Grain production in China has increased over time despite limited access to natural resources. However, this has led to China's grain supply system becoming increasingly vulnerable and unsustainable due to a northward shift of its grain production. Here, we establish a framework to guide future grain policy formulation in response to previous practices and lessons learned from China's past grain production. This framework integrated the spatial gravity model, spatial mismatch index, logarithmic mean Divisia index (LMDI), and Monte Carlo simulation to identify the key drivers behind grain growth, analyze their impacts on food security, and propose countermeasures. We found that grain production increase in China is not universally attributable to increased input of farmland and water resources, but rather, socio-economic factors including agricultural technology and irrigation facilities have improved efficiency. The spatial heterogeneity in their driving effects in different major grain producing regions has led grain production to shifted to the northern regions that have few natural resources, posing new challenges for food security: without new policies, China will not be poised to meet increased grain demand projected from 2025 to 2030, especially for rice and soybeans. From a comparison across four grain policies, it is found that region-specific policies will most effectively accelerate transitions to sustainable food production systems. We urge decision-makers to reach beyond natural resource inputs and focus on socio-economic factors, particularly inputs for replanting abandoned farmland and irrigation facilities that can ensure food security in the future.

Kinerja Ekspor Produk Teh Indonesia di Pasar Internasional: Asesmen Perjanjian Perdagangan Indonesia

The decline in Indonesian tea products export performance does not correspond to the Government initiatives to reduce barriers through trade agreements. This research aims to analyse the export performance and the role of trade agreements towards Indonesian tea products export. This study employs panel data regression with a 15-year time series (2007-2021) and a cross-section of 40 destination countries. The data are analysed using a modified export approach gravity model with Poisson Pseudo-Maximum Likelihood (PPML) estimation. The research results show that the Indonesian tea products export destinations are dominated by Asia (19 countries) and Europe (12 countries). The regression results suggest that the implementation of trade agreements with Asian and European region countries has not effectively increased Indonesian tea products export. On the other hand, the implementation of trade agreements with other region countries, i.e., Australia and New Zealand, has successfully promoted export towards Indonesian tea products. Those can be attributed to trade agreements underutilization and trade barriers imposed by the trade agreement members. Hence, inward and outward-looking strategies are necessary to promote the export creation effect of implemented trade agreements towards Indonesian tea product exports.

Estimating inter-regional trade: the radiation model versus the gravity model

The estimation of interregional trade flows within a country is confined to the context of multi-regional input–output models. Despite the remarkable relevance of these trade flows for regional incomes, most countries have almost no official data, with Korea being an exception used here. In addition to survey-based estimation methods, there are non-survey methods, some based on gravity models, which can be used to estimate inter-regional trade flows. This paper compares the gravity model with the novel radiation model. Preliminary results show that the accuracy of the radiation model’s estimation is superior to that of the gravity model, with the invaluable benefit of not needing to estimate regression coefficients, unlike the gravity model. This finding provides a generalisation of the radiation model for estimating interregional trade in contexts where there is no prior multi-regional input–output table without restrictions derived from coefficient estimation as in the gravity model.

A Coordination Analysis on Rural Revitalization and Tourism High-Quality Development along the Silk Road Economic Belt, China

There is limited analysis of the role of tourism in rural revitalization (RR) from a high-quality development perspective. To address this gap, this study analyzes the spatiotemporal patterns and coupling coordination degree (CCD) of tourism high-quality development (THD) and RR in the Silk Road Economic Belt from 2011 to 2020 using coupling coordination and gravity models. A geographic detector is employed to quantitatively elucidate the factors influencing the CCD. The findings are as follows. (1) The comprehensive RR level increased 86% from 2011 to 2020, whereas the THD level first increased and then decreased. The southwest region outperformed the northwest in RR and THD levels. (2) The CCD between RR and THD displayed various degrees of increase, with a spatial pattern of higher levels in the southwest and lower levels in the northwest. The spatial linkage strength of the CCD first increased and then decreased, with tighter linkages among the southwestern provinces. (3) Public fiscal expenditure, per capita GDP, and science and education spending significantly affected the CCD. In conclusion, the effective coordination of THD and RR requires a focus on their spatiotemporal coupling characteristics and the joint regulation of multiple factors.

The Role of Time Zone Differences on Bilateral Service Flows from Kenya

ABSTRACT This study investigates the effect of time zone differences on service exports (total and nine categories—travel, transport, computer and information, construction, financial, insurance, government, other business services, and personal, cultural, and recreational services) from Kenya. Estimates from the Poisson Pseudo-Maximum Likelihood (PPML) estimator of the gravity model on bilateral service exports data from Kenya to 176 countries, for the period 2005–2019, show that the effects of time zone differences between Kenya and partner countries is positive and statistically significant in technology-sensitive service exports (computer and information) while negative for construction and government service exports. Further analysis shows that these results are robust when an alternative model is employed and overlapping workday hours are used. The authors also find that the effect of time zone differences on services is nonlinear and sensitive to regulations and physical infrastructure (particularly mobile subscriptions). Attracting investment in technology-sensitive sectors should be encouraged through appropriate policy, given the positive impact of time zone differences on their exports. Traders in these sectors can also create networks with foreign firms. Deregulating and developing information and communication infrastructure, to expand mobile subscriptions, should also be encouraged.

Decoding air passenger flows: Identifying the role of network autocorrelation in air travel

With the rapid expansion of the global aviation industry, especially in the Eurasian continent, understanding the factors driving interregional air passenger flow is of increasing importance. While most existing studies emphasize node-level and edge-level influencing factors such as economic scale, population size, and geographic distance, they often neglect the pivotal variable of network autocorrelation. This research is the first to introduce network autocorrelation within the Eurasian context and systematically analyze it using the Eigenvector Spatial Filtering Negative Binomial Gravity Model. Our findings highlight: (1) A significant network autocorrelation in the Eurasian continental aviation network. The eigenvector spatial filtering negative binomial regression model effectively captures this autocorrelation, considerably reducing model estimation bias. Specifically, the leading 3.28% of eigenvectors capture a high degree of this network autocorrelation. (2) The presence of network autocorrelation introduces estimation biases in related variables, resulting in underestimations of economic size, population size, visa restriction, and international trade, while overestimating cultural and institutional differences, geographical distance, colonial relationship. (3) Various factors affect the Eurasian continental sub-region's air passenger flows differently, indicating regional variations. This study takes a step towards improving our understanding of network autocorrelation in air passenger flows research.

Spatial network analysis of green electricity efficiency dynamics in the Yellow River Basin cities

Improving the green electricity efficiency (GEE), is an important issue for China's high-quality economic development. This study presents a spatial correlation network of urban GEE in the Yellow River Basin from 2012 to 2021, constructed using an improved gravity model. Social network analysis and the quadratic assignment procedure method are employed to analyze the spatial correlation characteristics and influencing factors. The findings indicate that urban GEE in the Yellow River Basin exhibits complex and stable network characteristics. The spatial network analysis reveals that Jiayuguan City, Dongying City, Dingxi City, Zibo City, and Shizuishan City occupy central positions within the network. The results indicate that spatial adjacency, GDP per capita, industrial structure, and the level of science and technology expenditure are positively related to urban GEE, while environmental regulation and average temperature are negatively related. The findings of the study have led to policy recommendations aimed at enhancing urban GEE in the Yellow River Basin.

A New Combination Approach for Gibbs Phenomenon Suppression in Regional Validation of Global Gravity Field Model: A Case Study in North China

A global gravity field model (GGM) is essential to be validated with ground-based or airborne observational data for the accurate application of the GGM at a regional scale. Furthermore, accurately understanding the commission errors between the GGM and observational data are crucial for improving regional gravity fields. Taking the North China region as an example, to circumvent the omission errors, it is necessary to unify the spatial resolutions of the EIGEN-6C4 model and terrestrial gravity observational data to 110 km (determined by the distribution of gravity stations) by employing the spherical harmonic function for the EIGEN-6C4 model and the Slepian basis function for the gravity data, respectively. However, the application of spherical harmonic function expansions in the gravity model results in the Gibbs phenomenon, which may be a primary factor contributing to commission errors and impedes the accurate validation of the EIGEN-6C4 model with terrestrial gravity data. To effectively mitigate this issue, this study proposes a combination approach of window function filtering and regional eigenvalue constraint (based on the Slepian basis). Utilizing the EIGEN-6C4 gravity model to derive the gravity disturbance field at a resolution of 110 km (with spherical harmonic expansion up to the 180th degree and order), the combination approach effectively suppresses over 90% of high-degree (above the 120th degree) Gibbs phenomena. This approach also reduces signal leakage outside the region, thus enhancing the spatial accuracy of the regional gravity disturbance field. A subsequent comparison of the regional gravity disturbance field derived from the true model and terrestrial gravity data in North China indicates excellent consistency, with a root mean squared error (RMSE) of 0.80 mGal. This validation confirms that the combined approach of window function filtering and regional eigenvalue constraints effectively mitigates the Gibbs phenomenon and yields precise regional gravity fields. This approach is anticipated to significantly benefit scientific applications such as improving the accuracy of regional elevation benchmarks and accurately inverting the Earth’s internal structure.

Constraints on the parameters of modified Chaplygin–Jacobi and modified Chaplygin–Abel gases in f(T) gravity

In this work, we explore the parameter constraints of two dark energy models, namely the Modified Chaplygin–Jacobi gas (MCJG) and Modified Chaplygin–Abel gas (MCAG), within the context of [Formula: see text] gravity model in a non-flat Friedmann–Lemaître–Robertson–Walker (FLRW) universe. Our investigation involves comparing the equation of state for the MCJG and MCAG dark energy models with the equation of state derived from the [Formula: see text] gravity model. To derive constraints for the dark energy and [Formula: see text] gravity models, we use recent astronomical datasets, including [Formula: see text] data, type Ia supernovae observations, Gamma Ray Bursts data, quasar data, and Baryon Acoustic Oscillation (BAO) measurements. We present the reduced Hubble parameter in terms of observable parameters such as [Formula: see text] (density parameter of radiation), [Formula: see text] (density parameter of dark matter), [Formula: see text] (density parameter associated with spatial curvature), [Formula: see text] (density parameter of Modified Chaplygin–Jacobi gas), [Formula: see text] (density parameter of Modified Chaplygin–Abel gas), and [Formula: see text] (present value of the Hubble parameter). We explore the cosmological evolution through various cosmic diagnostic parameters, including the deceleration parameter, [Formula: see text] diagnostic, and statefinder diagnostic pair [Formula: see text]. These diagnostic parameters offer valuable insights into the expansion dynamics and the nature of dark energy in the universe. We have also assessed the viability of the models using the information criteria. Our aim is to shed light on the nature of dark energy and its connection to the [Formula: see text] gravity model, and ultimately gain a deeper understanding of the underlying mechanisms driving the accelerated expansion of our universe.

Constraining modified gravity scenarios with the 6dFGS and SDSS galaxy peculiar velocity data sets

ABSTRACT The detailed nature of dark energy remains a mystery, leaving the possibility that its effects might be explained by changes to the laws of gravity on large scales. The peculiar velocities of galaxies directly trace the strength of gravity on cosmic scales and provide a means to further constrain such models. We generate constraints on different scenarios of gravitational physics by measuring peculiar velocity (PV) and galaxy clustering two-point correlations, using redshifts and distances from the 6-degree Field Galaxy Survey and the Sloan Digital Sky Survey PV samples, and fitting them against models characteristic of different cosmologies. Our best-fitting results are all found to be in statistical agreement with general relativity, in which context we measure the low-redshift growth of structure to be $f\sigma _8 = 0.329^{+0.081}_{-0.083}$, consistent with the prediction of the standard Lambda cold dark matter model. We also fit the modified gravity scenarios of Dvali–Gabadadze–Porrati and a Hu–Sawicki model of $f(R)$ gravity, finding the $2\sigma$ limit of their characteristic parameters to be $r_{\rm c}H_0/c\gt 6.987$ and $-\log _{10}(|f_{R0}|)\gt 4.703$, respectively. These constraints are comparable to other literature values, though it should be noted that they are significantly affected by the prior adopted for their characteristic parameters. When applied to much larger upcoming PV surveys such as DESI, this method will place rapidly improving constraints on modified gravity models of cosmic expansion and growth.

Intra‐African trade and corruption: Evidence from sub‐Saharan African countries

AbstractCross‐border trade is critical to livelihoods and food security in sub‐Saharan Africa (SSA), but bribery remains one of the main barriers to economic growth in the region. Does corruption affect intra‐African trade? We address this issue by considering the bilateral trade among 48 sub‐Saharan African countries from 2000 to 2018, which are subject to a high level of corruption. Using a gravity model, the results show that corruption has a positive impact on exports and a negative impact on imports of global, primary, and manufactured goods. However, the difference in the level of corruption between country pairs is negatively and significantly associated with intra‐African trade in manufactured goods. Therefore, to promote the corruption‐free environment needed to facilitate the African Free Trade Agreement, it is essential for policymakers in sub‐Saharan African countries to combat corruption to boost intra‐African trade.

The non-minimally coupled symmetric teleparallel gravity with electromagnetic field

We construct a symmetric teleparallel gravity model which is non-minimally coupled with electromagnetic field in four dimensions inspired by its Riemannian equivalent. We derive the field equations by taking the variation of this model, which is written here for the first time. Then, we find some classes of spherically symmetric static solutions by the coincident gauge of symmetric teleparallel spacetime.

Study on the Impact of State Relations on Chinas Industrial Supply Chain Upstream from the Perspective of International Trade: A Case Study of Mineral Resources

As a major global power, Chinas overseas interests are rapidly expanding. Ensuring the security of industrial supply chains has become a critical issue. This paper adopts the perspective of international trade, utilizing the random frontier gravity model, and focuses on the top five mineral products and raw materials exported from China to India according to the 2019 export composition table of the Ministry of Commerce of the Peoples Republic of China. Based on export data of these minerals from China to India between 2008 and 2023, this paper analyzes the trends in mineral import and export, studies the correlation between bilateral trade between China and India and changes in Sino-Indian relations, and points out the potential impact of current Sino-Indian relations on Chinas upstream industrial chain. The study finds that for mineral fuels, mineral oils and their products, asphalt, zinc and its products, and steel products, Sino-Indian relations have a relatively minor impact on Chinas imports of such minerals and raw materials from India. However, for steel resources, Sino-Indian relations show a significant positive correlation with their import situation. Based on the current state of Sino-Indian relations, the study will propose relevant recommendations for the production and export of Indian steel and other mineral resources, combined with the needs of Chinas upstream industrial supply chain. This study aims to provide relevant insights and references for safeguarding Chinas strategic mineral resource security.

A sectoral analysis of a developing country's exports in the context of trade integration: Evidence from Colombia

The research delves into the effectiveness of Colombia's trade liberalisation process in boosting its exports at the industrial level. Based on an empirical workhorse approach to international trade, the gravity model, we evaluate the effect of trade openness on Colombian exports at the industrial level following the SITC4 categorisation. For this purpose, panel data on Colombian exports to all its trading partners between 2007 and 2020 were used. The results establish that Colombia's trade openness has boosted the exports of most of its industries, except for exports of the mineral fuels, lubricants and related materials group, which is a group of goods that represents the country's largest exports. Furthermore, the research also confirms the prominent impact of labour productivity in boosting Colombian exports of most product groups. Consequently, Colombian policymakers should support a re-composition of the Colombian export basket in order to take proper advantage of trade integration formulas, within a global energy transition framework.

The EU–UK Trade and Cooperation Agreement: A short and long-term comprehensive analysis including FDI

This study thoroughly assesses the impact of Brexit through trade, combining a static and dynamic computable general equilibrium (CGE) model and a structural gravity model. Our analysis allows us to shed light on the role of trade and the potential effects of foreign direct investment (FDI), which has received less attention in the context of Brexit. We simulate a hard Brexit and the new trade and cooperation agreement negotiated by Boris Johnson. We analyse several reductions in the United Kingdom's (UK) capital stock, consistent with the empirical evidence on potential reductions in the FDI capital stock after Brexit. This approach allows us to disentangle the effects of trade's static (short-term) impact from its dynamic (long term) impact. We focus on the impact for the UK but offer macro-economic results for the European Union (including individual countries), the United States, China and the rest of the world. The gravity model estimates considerably larger contractions in the UK's gross domestic product but a smaller role for FDI than the CGE. UK services sectors are affected more negatively than what previous analyses of Brexit focusing on trade suggest.