scholarly journals Gravity: Estimation Methods for Gravity Models in R

2018 ◽  
Vol 3 (31) ◽  
pp. 1038
Author(s):  
Anna-Lena Wölwer ◽  
Jan Burgard ◽  
Joshua Kunst ◽  
Mauricio Vargas
Keyword(s):  
Gravity Models ◽  
Estimation Methods ◽  
Gravity Estimation

scholarly journals Gravity Models in R

2018 ◽  
Vol 47 (4) ◽  
pp. 16-35 ◽  
Author(s):  
Anna-Lena Wölwer ◽  
Martin Breßlein ◽  
Jan Pablo Burgard
Keyword(s):  
Foreign Direct Investment ◽  
Direct Investment ◽  
Gravity Models ◽  
Estimation Methods ◽  
Research Topics ◽  
Cross Sectional ◽  
Interaction Costs ◽  
The Masses ◽  
Two Bodies

Gravity models are used to explain bilateral flows related to the sizes of bilateral partners, a measure of distance between them and other influences on interaction costs. The underlying idea is rather simple. The greater the masses of two bodies and the smaller the distance between them, the stronger they attract each other. This concept is applied to several research topics such as trade, migration or foreign direct investment. Even though the basic idea of gravity models is rather simple, they can become very complex when it comes to the choice of models or estimation methods. The package \textbf{gravity} targets to provide \proglang{R} users with the functions necessary to execute the most common estimation methods for gravity models, especially for cross-sectional data.   Gravitätsmodelle werden verwendet, um bilaterale Ströme zu erklären. Dabei werden sowohl die Größen und die Distanz der jeweiligen Partner als auch weitere Einflussfaktoren zur Erklärung herangezogen. Die zugrundeliegende Idee dieser Modelle beruht auf dem Gravitätsprinzip. Je schwerer zwei Körper und je kleiner deren Distanz zueinander, desto stärker ist ihre gegenseitige Anziehungskraft. Dieses Konzept wird auf verschiedene Forschungsreiche angewendet, so zum Beispiel Handel, Migration und ausländische Direktinvestitionen. Auch wenn die zugrundeliegende Idee von Gravitätsmodellen eher einfach ist, so kann deren Schätzung je nach Wahl des zugrundegelegten ökonomischen Zusammenhangs komplex werden. Das Paket \textbf{gravity} ermöglicht es \proglang{R}-Nutzern die gängigsten Verfahren für Gravitätsmodelle in der Querschnittsanalyse zu verwenden.

scholarly journals MATRIX RECOVERY METHODOLOGY BASED ON MOBILE DATA

2021 ◽  
Vol 2021 (1) ◽  
pp. 117-120
Author(s):  
Ol'ga Lebedeva
Keyword(s):  
Mobile Network ◽  
Gravity Models ◽  
Mobile Technologies ◽  
Estimation Methods ◽  
Reliable Estimate ◽  
Matrix Estimation ◽  
Advantages And Disadvantages ◽  
Consistent Assessment ◽  
Larger Sample

The study is aimed at comparing the methods of restoring the correspondence matrices and a more detailed study of the algorithm for restoring the correspondence matrix based on innovative mobile technologies. Previously, the correspondence matrices were reconstructed by interviewing vehicle drivers and applying gravity models, then matrix estimation methods are used to calculate traffic flows. Each of these approaches has a number of advantages and disadvantages, but there is no evidence to assess the quality of the data obtained. The results show that, in general, processing da-ta from the mobile network allows for a more reliable estimate without taking into account survey data or similar observations, and using this type of research can lead to a more consistent assessment of trips with a larger sample size

Gravity Models and Empirical Trade

2020 ◽  
Author(s):  
Scott Baier ◽  
Samuel Standaert
Keyword(s):  
International Trade ◽  
Market Structure ◽  
Gravity Model ◽  
Empirical Work ◽  
Gravity Models ◽  
Estimation Methods ◽  
Intuitive Appeal ◽  
Empirical Trade ◽  
Trade Frictions ◽  
Theoretical Developments

The gravity model of international trade states that the volume of trade between two countries is proportional to their economic mass and a measure of their relative trade frictions. Perhaps because of its intuitive appeal, the gravity model has been the workhorse model of international trade for more than 50 years. While the initial empirical work using the gravity model lacked sound theoretical underpinnings, the theoretical developments have highlighted how a gravity-like specification can be derived from many models with varying assumptions about preferences, technology, and market structure. Along the strengthening of the theoretical roots of the gravity model, the way in which it is estimated has also evolved significantly since the start of the new millennium. Depending on the exact characteristics of regression, different estimation methods should be used to estimate the gravity model.

scholarly journals COMPARATIVE ANALYSIS OF EXISTING METHODS FOR DEVELOPING CORRESPONDENCE MATRICES

2021 ◽  
Vol 1 (1) ◽  
pp. 181-182
Author(s):  
Ol'ga Lebedeva
Keyword(s):  
Comparative Analysis ◽  
Gravity Models ◽  
Mobile Technologies ◽  
Estimation Methods ◽  
Traffic Flows ◽  
Matrix Estimation ◽  
Advantages And Disadvantages

The study is aimed at comparing the methods of restoring correspondence matri ces, the traditional transport school and modern mobile technologies. Traditionally, correspondence matrices are restored by interviewing vehicle drivers and applying gravity models (to extrapolate and fill in unobserved movements), then matrix estimation methods are used to calculate traffic flows. Each of these approaches has a number of advantages and disadvantages, but there is no evidence to assess the quality of the data obtained.

The Impact of Missing and Error-Prone Auxiliary Information on Sparse-Matrix Sub-Population Parameter Estimates

Methodology ◽  
2015 ◽  
Vol 11 (3) ◽  
pp. 89-99 ◽  
Author(s):  
Leslie Rutkowski ◽  
Yan Zhou
Keyword(s):  
Sparse Matrix ◽  
Small Body ◽  
Auxiliary Information ◽  
Poor Quality ◽  
Quality Data ◽  
Estimation Methods ◽  
Parameter Estimates ◽  
Population Parameter ◽  
Conditioning Model ◽  
The Impact

Abstract. Given a consistent interest in comparing achievement across sub-populations in international assessments such as TIMSS, PIRLS, and PISA, it is critical that sub-population achievement is estimated reliably and with sufficient precision. As such, we systematically examine the limitations to current estimation methods used by these programs. Using a simulation study along with empirical results from the 2007 cycle of TIMSS, we show that a combination of missing and misclassified data in the conditioning model induces biases in sub-population achievement estimates, the magnitude and degree to which can be readily explained by data quality. Importantly, estimated biases in sub-population achievement are limited to the conditioning variable with poor-quality data while other sub-population achievement estimates are unaffected. Findings are generally in line with theory on missing and error-prone covariates. The current research adds to a small body of literature that has noted some of the limitations to sub-population estimation.

Femtocell Selection Scheme for Reducing Unnecessary Handover and Enhancing Downlink QoS in Cognitive Femtocell Networks

2017 ◽  
Author(s):  
Hoang Nhu Dong ◽  
Hoang Nam Nguyen ◽  
Hoang Trong Minh ◽  
Takahiko Saba
Keyword(s):  
Cellular Networks ◽  
Estimation Methods ◽  
Mobility Prediction ◽  
Capacity Estimation ◽  
Femtocell Networks ◽  
Selection Scheme ◽  
Indoor Communications ◽  
Performance Results ◽  
Cognitive Femtocell

Femtocell networks have been proposed for indoor communications as the extension of cellular networks for enhancing coverage performance. Because femtocells have small coverage radius, typically from 15 to 30 meters, a femtocell user (FU) walking at low speed can still make several femtocell-to-femtocell handovers during its connection. When performing a femtocell-to-femtocell handover, femtocell selection used to select the target handover femtocell has to be able not only to reduce unnecessary handovers and but also to support FU’s quality of service (QoS). In the paper, we propose a femtocell selection scheme for femtocell-tofemtocell handover, named Mobility Prediction and Capacity Estimation based scheme (MPCE-based scheme), which has the advantages of the mobility prediction and femtocell’s available capacity estimation methods. Performance results obtained by computer simulation show that the proposed MPCE-based scheme can reduce unnecessary femtocell-tofemtocell handovers, maintain low data delay and improve the throughput of femtocell users. DOI: 10.32913/rd-ict.vol3.no14.536

Biorefinery implementation for recovery debottlenecking at existing pulp mills- Part II: Techno-economic evaluation

TAPPI Journal ◽  
2012 ◽  
Vol 11 (8) ◽  
pp. 17-24 ◽  
Author(s):  
HAKIM GHEZZAZ ◽  
LUC PELLETIER ◽  
PAUL R. STUART
Keyword(s):  
Cost Estimation ◽  
Process Model ◽  
Black Liquor ◽  
Pulp Mill ◽  
Value Added ◽  
Economic Assessment ◽  
Extraction Process ◽  
Estimation Methods ◽  
Precipitation Process

The evaluation and process risk assessment of (a) lignin precipitation from black liquor, and (b) the near-neutral hemicellulose pre-extraction for recovery boiler debottlenecking in an existing pulp mill is presented in Part I of this paper, which was published in the July 2012 issue of TAPPI Journal. In Part II, the economic assessment of the two biorefinery process options is presented and interpreted. A mill process model was developed using WinGEMS software and used for calculating the mass and energy balances. Investment costs, operating costs, and profitability of the two biorefinery options have been calculated using standard cost estimation methods. The results show that the two biorefinery options are profitable for the case study mill and effective at process debottlenecking. The after-tax internal rate of return (IRR) of the lignin precipitation process option was estimated to be 95%, while that of the hemicellulose pre-extraction process option was 28%. Sensitivity analysis showed that the after tax-IRR of the lignin precipitation process remains higher than that of the hemicellulose pre-extraction process option, for all changes in the selected sensitivity parameters. If we consider the after-tax IRR, as well as capital cost, as selection criteria, the results show that for the case study mill, the lignin precipitation process is more promising than the near-neutral hemicellulose pre-extraction process. However, the comparison between the two biorefinery options should include long-term evaluation criteria. The potential of high value-added products that could be produced from lignin in the case of the lignin precipitation process, or from ethanol and acetic acid in the case of the hemicellulose pre-extraction process, should also be considered in the selection of the most promising process option.

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