ESSAYS ON INDUSTRIAL ORGANIZATION

This dissertation covers two topics within the context of the U.S. airline mergers. In Chapter 1, I develop a structural model to evaluate the effectiveness of alternative slot divestiture schemes in the US airline industry, focusing on the divestiture of slots at Ronald Reagan Washington National Airport (DCA), which the government required as a condition of the American/US Airways merger. Departing from the existing literature, my model accounts for how the number of slots allocated to a route segment affects carrier costs, how passengers going to many different destinations may use the same segments, and how carriers choose to allocate slots to segments. In Chapter 2, I use counterfactuals to show that slot divestitures can result in the re-allocation of surplus between consumers; to estimate the proportion of slots that the merged American would have needed to divest to maximize total welfare; and, to evaluate the effects of allocating divested slots to different types of carriers. I find that the proposed divestiture raised consumer surplus significantly ($112M per year) compared to approving the merger without divestiture, but that it re-allocated surplus between consumers in different markets. I also find that the policy of only allowing the slots to be divested to low-cost carriers raised consumer surplus relative to the policy of only allowing the slots to be divested to legacy carriers. In Chapter 3, my coauthors and I develop an airline route competition entry model in which carriers first choose whether to offer nonstop or connecting service and then choose prices. In this setting carriers’ quality and cost unobservables are known to every player throughout the game, so that carriers can self-select into choosing nonstop service. Accounting for selection when performing counterfactuals affects predictions about post-merger repositioning by rivals, likely price increases and the effectiveness of remedies, and allows the model to match observed changes after completed mergers

Air pollution and development in Africa: impacts on health, the economy, and human capital

Background Africa is undergoing both an environmental and an epidemiological transition. Household air pollution is the predominant form of air pollution, but it is declining, whereas ambient air pollution is increasing. We aimed to quantify how air pollution is affecting health, human capital, and the economy across Africa, with a particular focus on Ethiopia, Ghana, and Rwanda. Methods Data on household and ambient air pollution were from WHO Global Health Observatory, and data on morbidity and mortality were from the 2019 Global Burden of Disease Study. We estimated economic output lost due to air pollution-related disease by country, with use of labour income per worker, adjusted by the probability that a person (of a given age) was working. Losses were expressed in 2019 international dollars and as a proportion of gross domestic product (GDP). We also quantified the contribution of particulate matter (PM)2·5 pollution to intelligence quotient (IQ) loss in children younger than 10 years, with use of an exposure–response coefficient based on previously published data. Findings Air pollution was responsible for 1·1 million deaths across Africa in 2019. Household air pollution accounted for 697 000 deaths and ambient air pollution for 394 000. Ambient air pollution-related deaths increased from 361 000 in 2015, to 383 000 in 2019, with the greatest increases in the most highly developed countries. The majority of deaths due to ambient air pollution are caused by non-communicable diseases. The loss in economic output in 2019 due to air pollution-related morbidity and mortality was $3·02 billion in Ethiopia (1·16$1·63 billion in Ghana (0·95% of GDP), and $349 million in Rwanda (1·19% of GDP). PM2·5 pollution was estimated to be responsible for 1·96 billion lost IQ points in African children in 2019. Interpretation Ambient air pollution is increasing across Africa. In the absence of deliberate intervention, it will increase morbidity and mortality, diminish economic productivity, impair human capital formation, and undercut development. Because most African countries are still early in development, they have opportunities to transition rapidly to wind and solar energy, avoiding a reliance on fossil fuel-based economies and minimising pollution. Funding UN Environment Programme

Extremal Black Holes and Holographic C-Theorem

We found Bogomol'nyi type of the first order differential equations in three dimensional Einstein gravity and the effective second order ones in new massive gravity when an interacting scalar field is minimally coupled. Using these equations in Einstein gravity, we obtain analytic solutions corresponding to extremally rotating hairy black holes. We also obtain perturbatively extremal black hole solutions in new massive gravity using these lower order differential equations. All these solutions have the anti de-Sitter spaces as their asymptotic geometries and as the near horizon ones. This feature of solutions interpolating two anti de-Sitter spaces leads to the construction of holographic c-theorem in these cases. Since our lower order equations reduce naturally to the well-known equations for domain walls, our results can be regarded as the natural extension of domain walls to more generic cases.Comment: 1+31 pages, no figure, v2: some improvements, accepted for publication in Nucl. Phys.

Interactions between subjective memory complaint and objective cognitive deficit on memory performances

Background Subjective memory complaint (SMCs) is a common trait amongst older population. The subjective cognition about their memory could depend on objective cognition. The aim of the current study was to examine the interaction between subjective memory cognition (i.e., SMC) and objective cognition on cognitive functions in participants from older generation. Methods A total of 219 patients, 181 normal control (NC) patients and 38 patients with mild cognitive impairment (MCI), were examined through standardized and comprehensive clinical evaluation and neuropsychological assessment. The Subjective Memory Complaints Questionnaire was used to assess SMCs along with five cognitive tasks were used to evaluate cognitive decline over following areas: verbal memory, visuospatial memory, attention, fluency, and language. Results The results of 2 × 2 two-way analysis of variance (ANOVA) showed that there were significant interactions between SMCs and cognitive status (NC, MCI) on memory performances. NC with SMCs showed significantly lower performance in verbal memory and visuospatial memory compared to NCs without SMCs. Conversely, no effect was observed in the MCI group. Conclusion There are interactions between subjective cognition (i.e., SMC) and objective cognition (i.e., cognitive status) on memory performances in older adults. The roles of SMCs on memory performances should be interpreted with older adults objective cognitive status.This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (No. NRF-2017R1D1A1A02018479). This funding source had no role in the design of this study and will not have any role during its execution, analyses, interpretation of the data, or decision to submit result

AdS/BCFT Correspondence for Higher Curvature Gravity: An Example

We consider the effects of higher curvature terms on a holographic dual description of boundary conformal field theory. Specifically, we consider three-dimensional gravity with a specific combination of Ricci tensor square and curvature scalar square, so called, new massive gravity. We show that a boundary entropy and an entanglement entropy are given by similar expression with those of the Einstein gravity case when we introduce an {\it effective} Newton's constant and an {\it effective} cosmological constant. We also show that the holographic g-theorem still holds in this extension, and we give some comments about the central charge dependence of boundary entropy in the holographic construction. In the same way, we consider new type black holes and comment on the boundary profile. Moreover, we reproduce these results through auxiliary field formalism in this specific higher curvature gravity.Comment: 27pages, minor corrections, accepted in JHE

Holographic Renormalization and Stress Tensors in New Massive Gravity

We obtain holographically renormalized boundary stress tensors with the emphasis on a special point in the parameter space of three dimensional new massive gravity, using the so-called Fefferman-Graham coordinates with relevant counter terms. Through the linearized equations of motion with a standard prescription, we also obtain correlators among these stress tensors. We argue that the self-consistency of holographic renormalization determines counter terms up to unphysical ambiguities. Using these renormalized stress tensors in Fefferman-Graham coordinates, we obtain the central charges of dual CFT, and mass and angular momentum of some $AdS$ black hole solutions. These results are consistent with the previous ones obtained by other methods. In this study on the Fefferman-Graham expansion of new massive gravity, some aspects of higher curvature gravity are revealed.Comment: Version accepted for publication in JHEP, conclusion revised, references adde

Quasi Normal Modes for New Type Black Holes in New Massive Gravity

We obtain the quasi-normal mode frequencies of scalar perturbation on new type black holes in three dimensional new massive gravity. In some special cases, the exact quasi-normal mode frequencies are obtained by solving scalar field equations exactly. On some parameter regions, the highly damped quasi-normal mode frequencies are obtained in an analytic form by the so-called Stokes line method. This study on quasi-normal modes shed some light on the mysterious nature of these black holes. We also comment about AdS/CFT correspondence and the entropy/area spectrum for new type black holes.Comment: 21pages, 1figure; Published version, references are added, some parts are revise

Correction: The Minderoo-Monaco Commission on Plastics and Human Health

This article details a correction to: Landrigan PJ, Raps H, Cropper M, et al. The Minderoo-Monaco Commission on Plastics and Human Health. Annals of Global Health. 2023; 89(1): 23. DOI: https://doi.org/10.5334/aogh.4056

The Role of American Sign Language(ASL) in Paired Deaf Signers' Mathematics Learning through Computer Games

2015Many researchers have investigated how hearing kindergarteners explore technology-based tools (e.g., mathematics computer games) and interact with each other while playing computer games. However, we still know very little about how deaf kindergarteners interact and sign with each other while using technology-based tools. We conducted a case study of paired deaf signers learning number concepts playing mathematics computer games. We observed three different pairs for five months and videotaped sessions between two signers working on on-line mathematics computer games. The paired students American Sign Language competency was found to be critical for deaf kindergartners interaction to solve mathematical questions such as number concepts. Our findings also indicate that mathematics computer games can be a tool which can motivate deaf signers to communicate with each other and that in technology-based learning environments pairing would be a strategy to encourage deaf signers to interact with each other