The elasticity of trade : estimates and evidence

Quantitative results from a large class of structural gravity models of international trade depend critically on a single parameter governing the elasticity of trade with respect to trade frictions. We provide a new method to estimate this elasticity and illustrate the merits of our approach relative to the estimation strategy of Eaton and Kortum (2002). We employ this method on data for 123 developed and developing countries for the year 2004 using new disaggregate price and trade flow data. Our benchmark estimate for all countries is approximately 4.5, nearly 50 percent lower than the alternative estimation strategy would suggest. This difference implies a doubling of the measured welfare costs of autarky across a large class of widely used trade models

The Elasticity of Trade: Estimates and Evidence

Quantitative results from a large class of structural gravity models of international trade depend critically on the elasticity of trade with respect to trade frictions. We develop a new simulated method of moments estimator to estimate this elasticity from disaggregate price and trade-flow data and we use it within Eaton and Kortum's (2002) Ricardian model. We apply our estimator to disaggregate price and trade-flow data for 123 countries in the year 2004. Our method yields a trade elasticity of roughly four, nearly fifty percent lower than Eaton and Kortum's (2002) approach. This difference doubles the welfare gains from international trade.elasticity of trade, bilateral, gravity, price dispersion, indirect inference

Solving Large Extensive-Form Games with Strategy Constraints

Extensive-form games are a common model for multiagent interactions with imperfect information. In two-player zero-sum games, the typical solution concept is a Nash equilibrium over the unconstrained strategy set for each player. In many situations, however, we would like to constrain the set of possible strategies. For example, constraints are a natural way to model limited resources, risk mitigation, safety, consistency with past observations of behavior, or other secondary objectives for an agent. In small games, optimal strategies under linear constraints can be found by solving a linear program; however, state-of-the-art algorithms for solving large games cannot handle general constraints. In this work we introduce a generalized form of Counterfactual Regret Minimization that provably finds optimal strategies under any feasible set of convex constraints. We demonstrate the effectiveness of our algorithm for finding strategies that mitigate risk in security games, and for opponent modeling in poker games when given only partial observations of private information.Comment: Appeared in AAAI 201

The Elasticity of Trade: Estimates and Evidence

Quantitative results from a large class of international trade models depend critically on the elasticity of trade with respect to trade frictions. We develop a simulated method of moments estimator to estimate this elasticity from disaggregate price and trade-flow data using the Ricardian model. We motivate our estimator by proving that the estimator developed in Eaton and Kortum (2002) is biased in any finite sample. We quantitatively show that the bias is severe and that the data requirements necessary to eliminate it in practice are extreme. Applying our estimator to new disaggregate price and trade-flow data for 123 countries in the year 2004 yields a trade elasticity of roughly four, nearly fifty percent lower than Eaton and Kortum’s (2002) approach. This difference doubles the welfare gains from international trade.elasticity of trade, bilateral, gravity, price dispersion, indirect inference

Solving Games with Functional Regret Estimation

We propose a novel online learning method for minimizing regret in large extensive-form games. The approach learns a function approximator online to estimate the regret for choosing a particular action. A no-regret algorithm uses these estimates in place of the true regrets to define a sequence of policies. We prove the approach sound by providing a bound relating the quality of the function approximation and regret of the algorithm. A corollary being that the method is guaranteed to converge to a Nash equilibrium in self-play so long as the regrets are ultimately realizable by the function approximator. Our technique can be understood as a principled generalization of existing work on abstraction in large games; in our work, both the abstraction as well as the equilibrium are learned during self-play. We demonstrate empirically the method achieves higher quality strategies than state-of-the-art abstraction techniques given the same resources.Comment: AAAI Conference on Artificial Intelligence 201

First order Bragg grating filters in silicon on insulator waveguides.

The subject of this thesis is the design; analysis, fabrication and characterisation of first order Bragg Grating optical filters in Silicon-on-Insulator (SOI) planar waveguides. It is envisaged that this work will result in the possibility of Bragg Grating filters for use in Silicon Photonics. It is the purpose of the work to create as far as is possible flat surface waveguides so as to facilitate Thermo-Optic tuning and also the incorporation into rib-waveguide Silicon Photonics. The spectral response of the shallow Bragg Gratings was modelled using Coupled Mode Theory (CMT) by way of RSoft Gratingmod TM. Also the effect of having a Bragg Grating with alternate layers of refractive index 1.5 and 3.5 was simulated in order to verify that Silica and Silicon layered Bragg Gratings could be viable. A series of Bragg Gratings were patterned on 1.5 micron SOI at Philips in Eindhoven to investigate the variation of grating parameters with a) the period of the gratings b) the duty cycle (or mark to space ratio) of the gratings and c) the length of the region converted to Bragg Gratings (i.e. the number of grating period repetitions). One set of gratings were thermally oxidised at Philips in Eindhoven (this was to simulate the effects of oxidising Porous Silicon) and another set were ion implanted with Oxygen ions at the Ion Beam Facility, University of Surrey. The gratings were tested and found to give transmission minima at approximately 1540 nanometres and both methods of creating flat surfaces were found to give similar minima. Atomic Force Microscopy was applied to the grating area of the Ion as Implanted samples in the ATI, University of Surrey, which were found to have surface undulations in the order of 60 nanometres

Doxycycline or Ofloxacin for Outpatient Chlamydial Pelvic Inflammatory Disease? A Cost-Benefit and Cost-Effectiveness Analysis

Objective: The current Centers for Disease Control and Prevention (CDC) guidelines include 2 drugs, doxycycline and ofloxacin, for treatment of the chlamydial component of outpatient pelvic inflammatory disease (PID). Although ofloxacin costs about $90 more than doxycycline, doxycycline is frequently associated with side effects and patient compliance with this drug is probably poor. Because clinicians have little information by which to judge the tradeoffs between price and compliance for these 2 antibiotics, we examined the impact of patient compliance in the evaluation of the costs and benefits of using each drug

Partitions of codes

In this thesis we look at coding theory wherein we introduce the concept of perspective, a generalisation on the minimum distance of a code, which naturally leads to a partition of the code. Subsequently we introduce focused splittings, which shall be shown to be a generalisation of perfect codes. We investigate the existence of such objects, and address questions such as the complexity of finding a focused splittings, which we show to be NPComplete. We analyse the symmetries of focused splittings. We use focused splittings to address the problem of error correction and we construct an encoding method based on them. Finally we test this construction for various classes of focused splittings

Preserving Prairie: Restoring Fort Riley’s Grant Ridge

Alexander Gardner’s 1867 photograph of Fort Riley shows the fort protected by a massive ridge to the south - a classic Flint Hills escarpment. Named in honor of General Ulysses S. Grant, Grant Ridge formed the southern boundary of the original 1853 Fort Riley Military Reservation. (An introduction to the site of the 2013 Symphony in the Flint Hills.

Applying plant genomics to crop improvement

A report of the European Science Foundation-Wellcome Trust Conference on Crop Genomics, Trait Analysis and Breeding, Hinxton, UK, 8-11 November 2006