Counterfactual Sensitivity and Robustness

Researchers frequently make parametric assumptions about the distribution of unobservables when formulating structural models. Such assumptions are typically motived by computational convenience rather than economic theory and are often untestable. Counterfactuals can be particularly sensitive to such assumptions, threatening the credibility of structural modeling exercises. To address this issue, we leverage insights from the literature on ambiguity and model uncertainty to propose a tractable econometric framework for characterizing the sensitivity of counterfactuals with respect to a researcher's assumptions about the distribution of unobservables in a class of structural models. In particular, we show how to construct the smallest and largest values of the counterfactual as the distribution of unobservables spans nonparametric neighborhoods of the researcher's assumed specification while other `structural' features of the model, e.g. equilibrium conditions, are maintained. Our methods are computationally simple to implement, with the nuisance distribution effectively profiled out via a low-dimensional convex program. Our procedure delivers sharp bounds for the identified set of counterfactuals (i.e. without parametric assumptions about the distribution of unobservables) as the neighborhoods become large. Over small neighborhoods, we relate our procedure to a measure of local sensitivity which is further characterized using an influence function representation. We provide a suitable sampling theory for plug-in estimators and apply our procedure to models of strategic interaction and dynamic discrete choice

The Struggle for Security: Risk, Politics and Pension Policy in Ontario, 1960-2016

This dissertation traces the rise and decline of Ontarios workplace pension system that has resulted with growing emphasis on Canadas public pension system, focusing on the postwar period to 2016. Since the mid-1980s, workplace pension coverage in Ontario and across Canada has been decreasing, calling into question the ability of this system to provide adequate retirement income for future workers. Currently, large private and public sector employers such as Air Canada, General Motors Canada and Canada Post are seeking to replace secure defined benefit plans with less secure defined contribution plans. Given these trends, policymakers at the provincial and federal levels have attempted to remedy the insecurity produced by diminishing coverage rates. Using Ontario as a case study to examine Canadas retirement income system, this dissertation asks: Why has the risk of saving for retirement shifted, and what factors have driven this? Drawing from 22 semi-structure interviews with pension professionals, descriptive statistics, and Hansard Parliamentary transcriptions, several findings are established. First, although risk has been increasingly individualized since the 1990s, there is a limit to how much risk workers are willing to accept before political coalitions form to demand government play a larger role in establishing retirement income security. Risk transfer is thus contingent on union power, retiree activism, business lobbying, and the ideological position of governing parties. Second, the rise of individualized risk is generating new provincial/federal political dynamics in the field of pension policy, in which the failure of Canadas workplace pension systems is impacting the welfare state politics of Canada, pointing to the emergence of a new period of pension politics. This finding leads to the conclusion that in the field of pension policy in Canada, the assertion by risk theorists that globalizing forces are transforming the welfare/citizenship nexus away from a model premised on risk sharing to one in which the state must facilitate the needs of rational, risk taking citizens does not adequately describe recent trends in Canadian pension policymaking

New developments in FeynRules

The program FeynRules is a Mathematica package developed to facilitate the implementation of new physics theories into high-energy physics tools. Starting from a minimal set of information such as the model gauge symmetries, its particle content, parameters and Lagrangian, FeynRules provides all necessary routines to extract automatically from the Lagrangian (that can also be computed semi-automatically for supersymmetric theories) the associated Feynman rules. These can be further exported to several Monte Carlo event generators through dedicated interfaces, as well as translated into a Python library, under the so-called UFO model format, agnostic of the model complexity, especially in terms of Lorentz and/or color structures appearing in the vertices or of number of external legs. In this work, we briefly report on the most recent new features that have been added to FeynRules, including full support for spin-3/2 fermions, a new module allowing for the automated diagonalization of the particle spectrum and a new set of routines dedicated to decay width calculations.Comment: 6 pages. Contribution to the 15th International Workshop on advanced computing and analysis techniques (ACAT 2013), 16-21 May, Beijing, Chin

Reflections on the Struggle Against the Canada-US Free Trade Agreement (TFA), 30 Years Later

The implementation of the Canada-US Free Trade Agreement (CUSFTA) in January 1989 marked a decisive moment in the rise of neoliberalism as a political project in Canada. While the left, and socialist political economists in particular, played a central role in galvanizing opposition to the agreement and contributed in no small part to the demise of the Conservative government in 1993, the free trade agenda continued to move forward through the 1990s. This Special Issue revisits the history of struggles against free trade in Canada with two aims in mind: first to remember the coalitions through which opposition was organized, the mobilization of socialist critiques by activists and intellectuals, and the key events leading up to the adoption of the agreement. Second, drawing from this history to make sense of how things have changed over the past 30 years, as right-wing nationalists have increasingly taken the lead in opposing free trade, while neoliberals have sought to rebrand their project as ‘progressive’.  How can those on the left effectively confront the project of free trade today while at the same time challenging both far-right nationalism and neoliberal globalization

Geochemistry, Geothermobarometry and Geochronology of High-Pressure Granulites and Implications for the Exhumation History of Ultrahigh-Pressure Terranes: Dulan, Western China

The Dulan ultrahigh-pressure (UHP) rocks of the North Qaidam terrane, Western China, represent continental crust that has been subducted ~100 km during continental collision. Adjacent granulites representing burial to ~50 km could either be overprinted eclogites or a separate high-pressure-high-temperature (HP-HT) granulite unit. Overprinted eclogites and HP-HT granulites imply different P-T-t paths for UHP rocks. Metamorphic conditions for the granulites are 750–880 °C and 14–17 kbar. Zircon U-Pb geochronology, REE patterns and Ti-in-zircon thermometry indicate an increase in temperature from ~800 °C (449 Ma) to ~900 °C (418 Ma). This temperature increase could explain the presence of granulite leucosomes and tonalites (419 Ma) interpreted to represent partial melts. The temperature increase coincides with the end of UHP metamorphism and may be related to exhumation of UHP rocks. These granulites represent a separate HP-HT unit from the thickened overriding crust in a continental collision zone, above subducting UHP rocks

A superspace module for the FeynRules package

We describe an additional module for the Mathematica package FeynRules that allows for an easy building of any N=1 supersymmetric quantum field theory, directly in superspace. After the superfield content of a specific model has been implemented, the user can study the properties of the model, such as the supersymmetric transformation laws of the associated Lagrangian, directly in Mathematica. While the model dependent parts of the latter, i.e., the soft supersymmetry-breaking Lagrangian and the superpotential, have to be provided by the user, the model independent pieces, such as the gauge interaction terms, are derived automatically. Using the strengths of the Feynrules program, it is then possible to derive all the Feynman rules associated to the model and implement them in all the Feynman diagram calculators interfaced to FeynRules in a straightforward way.Comment: 54 pages, 9 tables, version accepted by CP

Variation in Food Prices and SNAP Adequacy for Purchasing the Thrifty Food Plan

Whether Supplemental Nutrition Assistance Program (SNAP) benefits are adequate to provide food security for eligible households is an important and timely policy question. While the nominal value of SNAP benefits is fixed across states (except for Hawaii and Alaska), variation in food prices across geographic areas is dramatic, and the real value of SNAP benefits varies widely across the U.S. Our research provides new evidence on geographic variation in the adequacy of SNAP benefits to purchase the Thrifty Food Plan (TFP). Using multiple methods to estimate the cost of the Thrifty Food Plan (TFP) faced by households across the nation, and several measures of the SNAP benefits available to them, we consistently find that a substantial fraction of SNAP-recipient households receive benefits that are insufficient to purchase the TFP. Our primary estimates indicate that SNAP benefits (plus 30 percent of income) are insufficient for approximately 20-30 percent of households to purchase the TFP. Sufficiency rates increase monotonically as we expand the distance within which the household is assumed to be able to shop. For households who are unable to afford the TFP, average dollar shortfalls between the cost of the TFP and SNAP benefits (plus 30 percent of income) are often as large as $150 per month. When shoppers are assumed to be able to purchase the TFP at the minimum-cost store in the area, SNAP benefits are sufficient for over 90 percent of households. However, this assumption seems unlikely to hold for many SNAP households

Altered brain energetics induces mitochondrial fission arrest in Alzheimer's Disease.

Altered brain metabolism is associated with progression of Alzheimer's Disease (AD). Mitochondria respond to bioenergetic changes by continuous fission and fusion. To account for three dimensional architecture of the brain tissue and organelles, we applied 3-dimensional electron microscopy (3D EM) reconstruction to visualize mitochondrial structure in the brain tissue from patients and mouse models of AD. We identified a previously unknown mitochondrial fission arrest phenotype that results in elongated interconnected organelles, "mitochondria-on-a-string" (MOAS). Our data suggest that MOAS formation may occur at the final stages of fission process and was not associated with altered translocation of activated dynamin related protein 1 (Drp1) to mitochondria but with reduced GTPase activity. Since MOAS formation was also observed in the brain tissue of wild-type mice in response to hypoxia or during chronological aging, fission arrest may represent fundamental compensatory adaptation to bioenergetic stress providing protection against mitophagy that may preserve residual mitochondrial function. The discovery of novel mitochondrial phenotype that occurs in the brain tissue in response to energetic stress accurately detected only using 3D EM reconstruction argues for a major role of mitochondrial dynamics in regulating neuronal survival

The availability of a functional tumor targeting T-cell repertoire determines the anti-tumor efficiency of combination therapy with anti-CTLA-4 and anti-4-1BB antibodies

It has previously been found that combination therapy with anti-CTLA-4 and anti-4-1BB antibodies may enhance tumor immunity. However, this treatment is not efficient against all tumors, and it has been suggested that variations in tumor control may reflect differences in the immunogenicity of different tumors. In the present report, we have formally tested this hypothesis. Comparing the efficiency of combination antibody therapy against two antigenically distinct variants of the B16.F10 melanoma cell line, we observed that antibody therapy delayed the growth of a variant expressing an exogenous antigen (P<0.0001), while this treatment failed to protect against the non-transfected parental line (P = 0.1850) consistent with published observations. As both cell lines are poorly immunogenic in wild type mice, these observations suggested that the magnitude of the tumor targeting T-cell repertoire plays a major role in deciding the efficiency of this antibody treatment. To directly test this assumption, we made use of mice expressing the exogenous antigen as a self-antigen and therefore carrying a severely purged T-cell repertoire directed against the major tumor antigen. Notably, combination therapy completely failed to inhibit tumor growth in the latter mice (P = 0.8584). These results underscore the importance of a functionally intact T-cell population as a precondition for the efficiency of treatment with immunomodulatory antibodies. Clinically, the implication is that this type of antibody therapy should be attempted as an early form of tumor-specific immunotherapy before extensive exhaustion of the tumor-specific T-cell repertoire has occurred