The determinants of democracy: a sensitivity analysis

Abstract Numerous studies—operating with diverse model specifications, samples and empirical measures—suggest different economic, social, cultural, demographic, institutional and international determinants of democracy. We distinguish between democratization and democratic survival and test the sensitivities of 67 proposed determinants by varying the control variable set, democracy measure, and sample time period. Furthermore, we go beyond existing sensitivity analyses and unpack the aggregate results by analyzing how theoretically motivated control variables affect sensitivity for two prominent determinants in the democracy literature: income and Islam. Overall, our results reveal a far larger number of robust determinants of democratization than of democratic survival. For democratic survival, the only robust factors are income and a law-abiding bureaucracy. In addition, our results highlight uncertainty surrounding the relationship between income and democratization, but show that broader development processes enhance the chances of democratization. Moreover, chances of democratization are lower in countries with large Muslim populations, but that relationship is sensitive to controlling for natural resources, education and neighborhood characteristics. Other results of the sensitivity analysis show that political protests, a democratic neighborhood, and the global proportion of democracies positively influence democratization, while natural resources, majoritarian systems, and long-tenured leaders make countries less likely to democratize.

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The Regime Debate Revisted: A Sensitivity Analysis of Democracy's Economic Effect

British Journal of Political Science ◽

10.1017/s0007123404000225 ◽

2004 ◽

Vol 34 (4) ◽

pp. 635-655 ◽

Cited By ~ 38

Author(s):

JONATHAN KRIECKHAUS

Keyword(s):

Sensitivity Analysis ◽

Statistical Significance ◽

Economic Effect ◽

Sensitivity Analyses ◽

Control Variables ◽

Time Period ◽

Negative Effect ◽

The 1960S ◽

Positive Effect ◽

Effect On Growth

Some studies find that democracy inhibits growth while other studies find that democracy facilitates growth. Which conclusion is correct? To help resolve this debate, a variety of sensitivity analyses is conducted to answer two basic questions. First, why has the literature yielded contradictory results? Secondly, how believable are these results? The existing contradictions can be explained by analysts' choice of time period, with democracy having a negative effect on growth in the 1960s, a positive effect in the 1980s and no effect at all in the 1970s and 1990s. More generally, however, it is shown here that the statistical significance of these findings varies radically depending upon which control variables one utilizes and how one measures both growth and democracy.

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IMMU-04. IMMUNE-RELATED ADVERSE EVENTS STRONGLY PREDICT SUPERIOR OUTCOMES IN BRAIN METASTASES PATIENTS RECEIVING LOCAL TREATMENT AND IMMUNE CHECKPOINT INHIBITORS

Neuro-Oncology ◽

10.1093/neuonc/noaa215.435 ◽

2020 ◽

Vol 22 (Supplement_2) ◽

pp. ii105-ii105

Author(s):

Alexander Hulsbergen ◽

Asad Lak ◽

Yu Tung Lo ◽

Nayan Lamba ◽

Steven Nagtegaal ◽

...

Keyword(s):

Sensitivity Analysis ◽

Adverse Events ◽

Brain Metastases ◽

Immune Checkpoint ◽

Immune Checkpoint Inhibitors ◽

Checkpoint Inhibitors ◽

Local Treatment ◽

Sensitivity Analyses ◽

Immortal Time Bias ◽

The Brain

Abstract INTRODUCTION In several cancers treated with immune checkpoint inhibitors (ICIs), a remarkable association between the occurrence of immune-related adverse events (irAEs) and superior oncological outcomes has been reported. This effect has hitherto not been reported in the brain. This study aimed to investigate the relation between irAEs and outcomes in brain metastases (BM) patients treated with both local treatment to the brain (LT; i.e. surgery and/or radiation) and ICIs. METHODS This study is a retrospective cohort analysis of patients treated for non-small cell lung cancer (NSCLC) BMs in a tertiary institution in Boston, MA. Outcomes of interest were overall survival (OS) and intracranial progression-free survival (IC-PFS), measured from the time of LT. Sensitivity analyses were performed to account for immortal time bias (i.e., patients who live longer receive more cycles of ICIs and thus have more opportunity to develop an irAE). RESULTS A total of 184 patients were included; 62 (33.7%) were treated with neurosurgical resection and 122 (66.3%) with upfront brain radiation. irAEs occurred in 62 patients (33.7%). After adjusting for lung-Graded Prognostic Assessment, type of LT, type of ICI, newly diagnosed vs. recurrent BM, BM size and number, targetable mutations, and smoking status, irAEs were strongly associated with better OS (HR 0.33, 95% CI 0.19 – 0.58, p < 0.0001) and IC-PFS (HR 0.41; 95% CI 0.26 – 0.65; p = 0.0001). Landmark analysis including only patients who received more than 3 cycles of ICI (n = 133) demonstrated similar results for OS and IC-PFS, as did sensitivity analysis adjusting for the number of cycles administered (HR range 0.36 – 0.51, all p-values < 0.02). CONCLUSIONS After adjusting for known prognostic factors, irAEs strongly predict superior outcomes after LT in NSCLC BM patients. Sensitivity analysis suggests that this is unlikely due to immortal time bias.

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Optimal tuned direct adaptive controller for seismic protecting of structures

Journal of Intelligent Material Systems and Structures ◽

10.1177/1045389x20988784 ◽

2021 ◽

pp. 1045389X2098878

Author(s):

Amin Hosseini ◽

Touraj Taghikhany ◽

Milad Jahangiri

Keyword(s):

Sensitivity Analysis ◽

Adaptive Control ◽

Optimization Problem ◽

Adaptive Controller ◽

Sensitivity Analyses ◽

Building Structures ◽

Building Structure ◽

The Past ◽

Innovative Method ◽

Story Building

In the past few years, many studies have proved the efficiency of Simple Adaptive Control (SAC) in mitigating earthquakes’ damages to building structures. Nevertheless, the weighting matrices of this controller should be selected after a large number of sensitivity analyses. This step is time-consuming and it will not necessarily yield a controller with optimum performance. In the current study, an innovative method is introduced to tuning the SAC’s weighting matrices, which dispenses with excessive sensitivity analysis. In this regard, we try to define an optimization problem using intelligent evolutionary algorithm and utilized control indices in an objective function. The efficiency of the introduced method is investigated in 6-story building structure equipped with magnetorheological dampers under different seismic actions with and without uncertainty in the model of the proposed structure. The results indicate that the controller designed by the introduced method has a desirable performance under different conditions of uncertainty in the model. Furthermore, it improves the seismic performance of structure as compared to controllers designed through sensitivity analysis.

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Sensitivity analysis of a coupled hydrodynamic-vegetation model using the effectively subsampled quadratures method (ESQM v5.2)

Geoscientific Model Development ◽

10.5194/gmd-10-4511-2017 ◽

2017 ◽

Vol 10 (12) ◽

pp. 4511-4523 ◽

Cited By ~ 6

Author(s):

Tarandeep S. Kalra ◽

Alfredo Aretxabaleta ◽

Pranay Seshadri ◽

Neil K. Ganju ◽

Alexis Beudin

Keyword(s):

Sensitivity Analysis ◽

Kinetic Energy ◽

Turbulent Kinetic Energy ◽

Aquatic Vegetation ◽

Three Dimensional ◽

Sensitivity Analyses ◽

Stem Density ◽

Sobol Indices ◽

Plant Stem ◽

Wave Induced

Abstract. Coastal hydrodynamics can be greatly affected by the presence of submerged aquatic vegetation. The effect of vegetation has been incorporated into the Coupled Ocean–Atmosphere–Wave–Sediment Transport (COAWST) modeling system. The vegetation implementation includes the plant-induced three-dimensional drag, in-canopy wave-induced streaming, and the production of turbulent kinetic energy by the presence of vegetation. In this study, we evaluate the sensitivity of the flow and wave dynamics to vegetation parameters using Sobol' indices and a least squares polynomial approach referred to as the Effective Quadratures method. This method reduces the number of simulations needed for evaluating Sobol' indices and provides a robust, practical, and efficient approach for the parameter sensitivity analysis. The evaluation of Sobol' indices shows that kinetic energy, turbulent kinetic energy, and water level changes are affected by plant stem density, height, and, to a lesser degree, diameter. Wave dissipation is mostly dependent on the variation in plant stem density. Performing sensitivity analyses for the vegetation module in COAWST provides guidance to optimize efforts and reduce exploration of parameter space for future observational and modeling work.

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COST-EFFECTIVENESS ANALYSIS OF IVABRADINE IN TREATMENT OF PATIENTS WITH HEART FAILURE IN IRAN

International Journal of Technology Assessment in Health Care ◽

10.1017/s0266462318003598 ◽

2018 ◽

Vol 34 (6) ◽

pp. 576-583 ◽

Cited By ~ 2

Author(s):

Saeed Taheri ◽

Elham Heidari ◽

Mohammad Ali Aivazi ◽

Mehran Shams-Beyranvand ◽

Mehdi Varmaghani

Keyword(s):

Heart Failure ◽

Sensitivity Analysis ◽

Cost Effectiveness ◽

Incremental Cost ◽

Transition Probabilities ◽

Drug Acquisition ◽

Sensitivity Analyses ◽

Baseline Heart Rate ◽

Life Years ◽

The Cost

Objectives:This study aimed to assess the cost-effectiveness of ivabradine plus standard of care (SoC) in comparison with current SoC alone from the Iranian payer perspective.Methods:A cohort-based Markov model was developed to assess the incremental cost-effectiveness ratio (ICER) over a 10-year time horizon in a cohort of 1,000 patients. The baseline transition probabilities between New York Heart Association (NYHA), mortality rate, and hospitalization rate were extracted from the literature. The effect of ivabradine on mortality, hospitalization, and NYHA improvement or worsening were retrieved from the SHIFT study. The effectiveness was measured as quality-adjusted life-years (QALYs) using the utility values derived from Iranian Heart Failure Quality of Life study. Direct medical costs were obtained from hospital records and national tariffs. Deterministic and probabilistic sensitivity analyses were conducted to show the robustness of the model.Results:Ivabradine therapy was associated with an incremental cost per QALY of USD $5,437 (incremental cost of USD $2,207 and QALYs gained 0.41) versus SoC. The probabilistic sensitivity analysis showed that ivabradine is expected to have a 60 percent chance of being cost-effective accepting a threshold of USD $6,550 per QALY. Furthermore, deterministic sensitivity analysis indicated that the model is sensitive to the ivabradine drug acquisition cost.Conclusions:The cost-effectiveness model suggested that the addition of ivabradine to SoC therapy was associated with improved clinical outcomes along with increased costs. The analysis indicates that the clinical benefit of ivabradine can be achieved at a reasonable cost in eligible heart failure patients with sinus rhythm and a baseline heart rate ≥ 75 beats per minute (bpm).

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Adjoint-based parametric sensitivity analysis for swirling M-flames

Journal of Fluid Mechanics ◽

10.1017/jfm.2018.793 ◽

2018 ◽

Vol 859 ◽

pp. 516-542 ◽

Cited By ~ 2

Author(s):

Calum S. Skene ◽

Peter J. Schmid

Keyword(s):

Sensitivity Analysis ◽

Frequency Response ◽

Stokes Equations ◽

Numerical Study ◽

Computational Cost ◽

Base Flow ◽

Sensitivity Analyses ◽

Perturbation Expansions ◽

Mean Flow ◽

Adjoint Solutions

A linear numerical study is conducted to quantify the effect of swirl on the response behaviour of premixed lean flames to general harmonic excitation in the inlet, upstream of combustion. This study considers axisymmetric M-flames and is based on the linearised compressible Navier–Stokes equations augmented by a simple one-step irreversible chemical reaction. Optimal frequency response gains for both axisymmetric and non-axisymmetric perturbations are computed via a direct–adjoint methodology and singular value decompositions. The high-dimensional parameter space, containing perturbation and base-flow parameters, is explored by taking advantage of generic sensitivity information gained from the adjoint solutions. This information is then tailored to specific parametric sensitivities by first-order perturbation expansions of the singular triplets about the respective parameters. Valuable flow information, at a negligible computational cost, is gained by simple weighted scalar products between direct and adjoint solutions. We find that for non-swirling flows, a mode with azimuthal wavenumber $m=2$ is the most efficiently driven structure. The structural mechanism underlying the optimal gains is shown to be the Orr mechanism for $m=0$ and a blend of Orr and other mechanisms, such as lift-up, for other azimuthal wavenumbers. Further to this, velocity and pressure perturbations are shown to make up the optimal input and output showing that the thermoacoustic mechanism is crucial in large energy amplifications. For $m=0$ these velocity perturbations are mainly longitudinal, but for higher wavenumbers azimuthal velocity fluctuations become prominent, especially in the non-swirling case. Sensitivity analyses are carried out with respect to the Mach number, Reynolds number and swirl number, and the accuracy of parametric gradients of the frequency response curve is assessed. The sensitivity analysis reveals that increases in Reynolds and Mach numbers yield higher gains, through a decrease in temperature diffusion. A rise in mean-flow swirl is shown to diminish the gain, with increased damping for higher azimuthal wavenumbers. This leads to a reordering of the most effectively amplified mode, with the axisymmetric ($m=0$) mode becoming the dominant structure at moderate swirl numbers.

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Cost of coils for intracranial aneurysms: clinical decision analysis for implementation of a capitation model

Journal of Neurosurgery ◽

10.3171/2017.3.jns163149 ◽

2018 ◽

Vol 128 (6) ◽

pp. 1792-1798 ◽

Cited By ~ 3

Author(s):

Gurpreet S. Gandhoke ◽

Yash K. Pandya ◽

Ashutosh P. Jadhav ◽

Tudor Jovin ◽

Robert M. Friedlander ◽

...

Keyword(s):

Sensitivity Analysis ◽

Probabilistic Sensitivity Analysis ◽

Cost Savings ◽

Clinical Decision ◽

Sensitivity Analyses ◽

List Price ◽

Maximum Dimension ◽

Total Length ◽

The Mean ◽

Mean Cost

OBJECTIVEThe price of coils used for intracranial aneurysm embolization has continued to rise despite an increase in competition in the marketplace. Coils on the US market range in list price from $500 to $3000. The purpose of this study was to investigate potential cost savings with the use of a price capitation model.METHODSThe authors built a clinical decision analytical tree and compared their institution’s current expenditure on endovascular coils to the costs if a capped-price model were implemented. They retrospectively reviewed coil and cost data for 148 patients who underwent coil embolization from January 2015 through September 2016. Data on the length and number of coils used in all patients were collected and analyzed. The probabilities of a treated aneurysm being ≤/> 10 mm in maximum dimension, the total number of coils used for a case being ≤/> 5, and the total length of coils used for a case being ≤/> 50 cm were calculated, as was the mean cost of the currently used coils for all possible combinations of events with these probabilities. Using the same probabilities, the authors calculated the expected value of the capped-price strategy in comparison with the current one. They also conducted multiple 1-way sensitivity analyses by applying plausible ranges to the probabilities and cost variables. The robustness of the results was confirmed by applying individual distributions to all studied variables and conducting probabilistic sensitivity analysis.RESULTSNinety-five (64%) of 148 patients presented with a rupture, and 53 (36%) were treated on an elective basis. The mean aneurysm size was 6.7 mm. A total of 1061 coils were used from a total of 4 different providers. Companies A (72%) and B (16%) accounted for the major share of coil consumption. The mean number of coils per case was 7.3. The mean cost per case (for all coils) was $10,434. The median total length of coils used, for all coils, was 42 cm. The calculated probability of treating an aneurysm less than 10 mm in maximum dimension was 0.83, for using 5 coils or fewer per case it was 0.42, and for coil length of 50 cm or less it was 0.89. The expected cost per case with the capped policy was calculated to be $4000, a cost savings of $6564 in comparison with using the price of Company A. Multiple 1-way sensitivity analyses revealed that the capped policy was cost saving if its cost was less than $10,500. In probabilistic sensitivity analyses, the lowest cost difference between current and capped policies was $2750.CONCLUSIONSIn comparison with the cost of coils from the authors’ current provider, their decision model and probabilistic sensitivity analysis predicted a minimum $407,000 to a maximum $1,799,976 cost savings in 148 cases by adapting the capped-price policy for coils.

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Measuring the sensitivity of difference-in-difference estimates to the parallel trends assumption

Research Methods in Medicine & Health Sciences ◽

10.1177/26320843211061306 ◽

2021 ◽

pp. 263208432110613

Author(s):

Landon Gibson ◽

Frederick Zimmerman

Keyword(s):

Sensitivity Analysis ◽

Treatment Period ◽

Treatment Effect ◽

Statistical Tests ◽

Sensitivity Analyses ◽

Difference In Difference ◽

Control Groups ◽

Pre Treatment ◽

Background Difference ◽

And Control

Background. Difference-in-Difference makes a critical assumption that the changes in the outcomes, over the post-treatment period, are similar between the treated and control groups—the parallel trends assumption. Evaluation of this assumption is often done either by graphical examination or by statistical tests in the pre-treatment period. They result in a binary conclusion about the validity of the assumption. Purpose. This paper proposes a sensitivity analysis that quantifies the departure from parallel trends necessary to meaningfully change the estimated treatment effect. Results. Sensitivity analyses have an advantage over traditional parallel trends tests: they use all available data and thereby work even if only one pre-period is available, and they quantify the strength of unobserved confounder(s) required to change the conclusions of a study. Conclusions. We apply the sensitivity analysis metrics developed by Cinelli and Hazlett (2020) and illustrate them on two studies.

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Exergoeconomic and Normalized Sensitivity Analysis of Plate Heat Exchangers: A Theoretical Framework with Application

10.5772/intechopen.99736 ◽

2021 ◽

Author(s):

Muhammad Ahmad Jamil ◽

Talha S. Goraya ◽

Haseeb Yaqoob ◽

Kim Choon Ng ◽

Muhammad Wakil Shahzad ◽

...

Keyword(s):

Sensitivity Analysis ◽

Heat Exchangers ◽

Power Plants ◽

Theoretical Framework ◽

Plate Heat Exchanger ◽

Sensitivity Analyses ◽

Thermal Systems ◽

Plate Heat ◽

Economic Analyses ◽

Exergoeconomic Analysis

Heat exchangers are the mainstay of thermal systems and have been extensively used in desalination systems, heating, cooling units, power plants, and energy recovery systems. This chapter demonstrates a robust theoretical framework for heat exchangers investigation based on two advanced tools, i.e., exergoeconomic analysis and Normalized Sensitivity Analysis. The former is applied as a mutual application of economic and thermodynamic analyses, which is much more impactful than the conventional thermodynamic and economic analyses. This is because it allows the investigation of combinatory effects of thermodynamic and fiscal parameters which are not achieved with the conventional methods. Similarly, the Normalized Sensitivity Analysis allows a one-on-one comparison of the sensitivity of output parameters to the input parameters with entirely different magnitudes on a common platform. This rationale comparison is obtained by normalizing the sensitivity coefficients by their nominal values, which is not possible with the conventional sensitivity analyses. An experimentally validated example of a plate heat exchanger is used to demonstrate the application of the proposed framework from a desalination system.

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Intima heterogeneity in stress assessment of atherosclerotic plaques

Interface Focus ◽

10.1098/rsfs.2017.0008 ◽

2017 ◽

Vol 8 (1) ◽

pp. 20170008 ◽

Cited By ~ 5

Author(s):

Ali C. Akyildiz ◽

Lambert Speelman ◽

Bas van Velzen ◽

Raoul R. F. Stevens ◽

Antonius F. W. van der Steen ◽

...

Keyword(s):

Sensitivity Analysis ◽

Plaque Rupture ◽

Homogeneous Model ◽

Sensitivity Analyses ◽

Homogeneous Material ◽

Sensitivity Index ◽

Stress Assessment ◽

Heterogeneous Models ◽

Homogeneous Models ◽

Accuracy Stress

Atherosclerotic plaque rupture is recognized as the primary cause of cardiac and cerebral ischaemic events. High structural plaque stresses have been shown to strongly correlate with plaque rupture. Plaque stresses can be computed with finite-element (FE) models. Current FE models employ homogeneous material properties for the heterogeneous atherosclerotic intima. This study aimed to evaluate the influence of intima heterogeneity on plaque stress computations. Two-dimensional FE models with homogeneous and heterogeneous intima were constructed from histological images of atherosclerotic human coronaries ( n = 12). For homogeneous models, a single stiffness value was employed for the entire intima. For heterogeneous models, the intima was subdivided into four clusters based on the histological information and different stiffness values were assigned to the clusters. To cover the reported local intima stiffness range, 100 cluster stiffness combinations were simulated. Peak cap stresses (PCSs) from the homogeneous and heterogeneous models were analysed and compared. By using a global variance-based sensitivity analysis, the influence of the cluster stiffnesses on the PCS variation in the heterogeneous intima models was determined. Per plaque, the median PCS values of the heterogeneous models ranged from 27 to 160 kPa, and the PCS range varied between 43 and 218 kPa. On average, the homogeneous model PCS values differed from the median PCS values of heterogeneous models by 14%. A positive correlation ( R 2 = 0.72) was found between the homogeneous model PCS and the PCS range of the heterogeneous models. Sensitivity analysis showed that the highest main sensitivity index per plaque ranged from 0.26 to 0.83, and the average was 0.47. Intima heterogeneity resulted in substantial changes in PCS, warranting stress analyses with heterogeneous intima properties for plaque-specific, high accuracy stress assessment. Yet, computations with homogeneous intima assumption are still valuable to perform sensitivity analyses or parametric studies for testing the effect of plaque geometry on PCS. Moreover, homogeneous intima models can help identify low PCS, stable type plaques with thick caps. Yet, for thin cap plaques, accurate stiffness measurements of the clusters in the cap and stress analysis with heterogeneous cap properties are required to characterize the plaque stability.

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