The Cost Channel Reconsidered: A Comment Using an Identification-Robust Approach

We re-examine the empirical relevance of the cost channel of monetary policy (e.g. Ravenna and Walsh, 2006), employing recently developed moment-conditions inference methods, including identiÂ…cation-robust procedures. Using US data, our results suggest that the cost channel effect is poorly identiÂ…ed and we are thus unable to corroborate the previous results in the literatureCost channel, Phillips curve, GMM, Generalized Empirical Likelihood, Weak IdentiÂ…cation

Cointegration Tests under Multiple Regime Shifts: An Application to the Stock Price-Dividend Relationship

We examine the properties of several residual-based cointegration tests when long run parameters are subject to multiple shifts driven by an unobservable Markov process. Unlike earlier work, which considered one-off deterministic breaks, our approach has the advantage of allowing for an unspeci?ed number of stochastic breaks. We illustrate this issue by exploring the possibility of Markov switching cointegration in the stock-price dividend relationship and showing that this case is empirically relevant. Our subsequent Monte Carlo analysis reveals that standard cointegration tests are generally reliable, their performance often being robust for a number of plausible regime shift parameterizations.Present value model, Cointegration tests, Markov switching

The plateau of trials: modern ethnicity in Angola

This thesis is a study about the modern ethnicity of the Ovimbundu of the central highlands of Angola. It shows how Ovimbundu conceptions of ethnicity became altered and enhanced by processes of modernisation, usually introduced by foreign agents, and how this modernisation came to play a critical role after independence. Following a contrast in existing literature between either the attribution of vital importance to ethnicity in human agency or the downplay of it in favour of other elements, this work may be positioned in the middle, that is, it finds common ground with both arguments. I follow a constructivist approach, patent throughout the thesis and much used by many academic studies, which enables the analysis of Ovimbundu modern ethnicity by crossing the several influences the people of the central highlands were exposed to with their own agency and capacity to imagine and follow new ideas, mostly associated with modernisation. A paradigm begins emerging, one that recurs to the experiences apprehended during colonialism, influenced by processes of evangelisation and colonisation, which allow a clearer and more complete comprehension of aspects pertaining to the organisation of the political movements, the civil-war and issues related with post-war reconciliation, integration and state-formation. It becomes clear that the construction and imagination of political identities was much dependent upon processes of ethnic modernisation, which are still influential in people’s lives in contemporary Angola.Esta dissertação trata a etnicidade moderna dos Ovimbundu do planalto central de Angola, revelando o modo como as conceções de etnicidade dessa população foram alteradas por processos de modernização, frequentemente introduzidos por elementos externos ao grupo, e como esta modernização étnica veio a desempenhar um papel crítico, depois da independência do país. Este trabalho, seguindo um contraste na literatura existente entre a atribuição de uma importância bastante significativa à etnicidade na agência humana ou a minimização do seu impacto face a outros elementos explicativos, posiciona-se entre as duas abordagens, isto é, encontra um argumento comum entre as duas vertentes literárias. É adotada uma abordagem construtivista, patente em toda a tese e comumente utilizada em estudos académicos, que permite uma análise da etnicidade moderna dos Ovimbundu, cruzando as várias influências a que a população do planalto central esteve exposta com a sua própria agência e capacidade de imaginar e seguir novas ideias associadas à modernização. Começa então a surgir um paradigma, fruto das experiências apreendidas durante o colonialismo, influenciadas por processos de evangelização e colonização, que permitem uma compreensão mais clara e completa de aspetos relacionados com a organização dos movimentos políticos, a própria guerra civil e outros referentes a reconciliação no pós-guerra, integração e formação do estado. Ganha forma a ideia de que, ao longo da exposição dos argumentos, a construção e imaginação de identidades políticas dependem muito dos vários processos de modernização étnica, que são ainda influentes na vida das pessoas na Angola contemporânea

Types for X10 Clocks

X10 is a modern language built from the ground up to handle future parallel systems, from multicore machines to cluster configurations. We take a closer look at a pair of synchronisation mechanisms: finish and clocks. The former waits for the termination of parallel computations, the latter allow multiple concurrent activities to wait for each other at certain points in time. In order to better understand these concepts we study a type system for a stripped down version of X10. The main result assures that well typed programs do not run into the errors identified in the X10 language reference, namely the ClockUseException. The study will open, we hope, doors to a more flexible utilisation of clocks in the X10 language.Comment: In Proceedings PLACES 2010, arXiv:1110.385

Deductive Verification of Parallel Programs Using Why3

The Message Passing Interface specification (MPI) defines a portable message-passing API used to program parallel computers. MPI programs manifest a number of challenges on what concerns correctness: sent and expected values in communications may not match, resulting in incorrect computations possibly leading to crashes; and programs may deadlock resulting in wasted resources. Existing tools are not completely satisfactory: model-checking does not scale with the number of processes; testing techniques wastes resources and are highly dependent on the quality of the test set. As an alternative, we present a prototype for a type-based approach to programming and verifying MPI like programs against protocols. Protocols are written in a dependent type language designed so as to capture the most common primitives in MPI, incorporating, in addition, a form of primitive recursion and collective choice. Protocols are then translated into Why3, a deductive software verification tool. Source code, in turn, is written in WhyML, the language of the Why3 platform, and checked against the protocol. Programs that pass verification are guaranteed to be communication safe and free from deadlocks. We verified several parallel programs from textbooks using our approach, and report on the outcome.Comment: In Proceedings ICE 2015, arXiv:1508.0459

The cost channel reconsidered: a comment using an identification-robust approach

We re-examine the empirical relevance of the cost channel of monetary policy (e.g. Ravenna and Walsh, 2006), employing recently developed moment-conditions inference methods, including identification-robust procedures. Using US data, our results suggest that the cost channel effect is poorly identified and we are thus unable to corroborate the previous results in the literature.Cost channel; Phillips curve; GMM; Generalized Empirical Likelihood; Weak Identification.

The Forecast Performance of Long Memory and Markov Switching Models

Recent research has focused on the links between long memory and structural change, stressing the long memory properties that may arise in models with parameter changes. In this paper, we contribute to this research by comparing the forecasting abilities of long memory and Markov switching models. Two approaches are employed: a Monte Carlo study and an empirical comparison, using the quarterly Consumer Price inflation rate in Portugal in the period 1968-1998. Although long memory models may capture some in-sample features of the data, when shifts occur in the series considered, their forecast performance is relatively poor, when compared with simple linear and Markov switching models. Moreover, our findings, in a more general framework, are in accordance with the works of Clements and Hendry (1998) and Clements and Krolzig (1998), reinforcing the idea that simple linear time series models remain useful tools for prediction.Long Memory; Structural change; Forecasting

The Properties of Cointegration Tests in Models with Structural Change

In this paper we examine, by means of Monte Carlo simulation, the properties of several cointegration tests when long run parameters are subject to structural changes. We allow for different types of stochastic and deterministic regime shifts, more specifically, changes governed by Markov chains, martingale parameter variation, sudden multiple breaks and gradual changes. Our Monte Carlo analysis reveals that tests with cointegration as the null hypothesis perform badly, while tests with the null of no cointegration retain much of their usefulness in this context.Structural change; Cointegration; Tests; Monte Carlo

Incremental Cardinality Constraints for MaxSAT

Maximum Satisfiability (MaxSAT) is an optimization variant of the Boolean Satisfiability (SAT) problem. In general, MaxSAT algorithms perform a succession of SAT solver calls to reach an optimum solution making extensive use of cardinality constraints. Many of these algorithms are non-incremental in nature, i.e. at each iteration the formula is rebuilt and no knowledge is reused from one iteration to another. In this paper, we exploit the knowledge acquired across iterations using novel schemes to use cardinality constraints in an incremental fashion. We integrate these schemes with several MaxSAT algorithms. Our experimental results show a significant performance boost for these algo- rithms as compared to their non-incremental counterparts. These results suggest that incremental cardinality constraints could be beneficial for other constraint solving domains.Comment: 18 pages, 4 figures, 1 table. Final version published in Principles and Practice of Constraint Programming (CP) 201