Exploratory semiparametric analysis of two-dimensional diffusions in finance

We examine bivariate extensions of Aït-Sahalia’s approach to the estimation of univariate diffusions. Our message is that extending his idea to a bivariate setting is not straightforward. In higher dimensions, as opposed to the univariate case, the elements of the Itô and Fokker-Planck representations do not coincide; and, even imposing sensible assumptions on the marginal drifts and volatilities is not sufficient to obtain direct generalisations. We develop exploratory estimation and testing procedures, by parametrizing the drifts of both component processes and setting restrictions on the terms of either the Itô or the Fokker-Planck covariance matrices. This may lead to highly nonlinear ordinary differential equations, where the definition of boundary conditions is crucial. For the methods developed, the Fokker-Planck representation seems more tractable than the Itô’s. Questions for further research include the design of regularity conditions on the time series dependence in the data, the kernels actually used and the bandwidths, to obtain asymptotic properties for the estimators proposed. A particular case seems promising: “causal bivariate models” in which only one of the diffusions contributes to the volatility of the other. Hedging strategies which estimate separately the univariate diffusions at stake may thus be improved.

Contributions to the Theory of Optimal Tests

This paper considers tests which maximize the weighted average power (WAP). The focus is on determining WAP tests subject to an uncountable number of equalities and/or inequalities. The unifying theory allows us to obtain tests with correct size, similar tests, and unbiased tests, among others. A WAP test may be randomized and its characterization is not always possible. We show how to approximate the power of the optimal test by sequences of nonrandomized tests. Two alternative approximations are considered. The rst approach considers a sequence of similar tests for an increasing number of boundary conditions. This discretization allows us to implement the WAP tests in practice. The second method nds a sequence of tests which approximate the WAP test uniformly. This approximation allows us to show that WAP similar tests are admissible. The theoretical framework is readily applicable to several econometric models, including the important class of the curved-exponential family. In this paper, we consider the instrumental variable model with heteroskedastic and autocorrelated errors (HAC-IV) and the nearly integrated regressor model. In both models, we nd WAP similar and (locally) unbiased tests which dominate other available tests.

Conexão entre estratégia e conhecimento na criação de valor adicional para stekeholders expressivos: um nova forma de organizar os contextos capacitantes

Este trabalho tratar sobre estratégia e conhecimento, questionando o porquê das organizações deixarem de aproveitar os ativos de conhecimentos que transcendem aos definidos pela estratégia organizacional e que podem gerar valor adicional para seus stakeholders expressivos. Esses ativos de conhecimentos que estão além dos exigidos pelos cargos e funções, aqui denominados de “excedentes cognitivos”, permitiriam induzir flexibilidade estratégica, criar recursos intangíveis distintivos e gerar valor adicional. Entretanto, a lógica da estratégia tradicional, baseada na eficiência e na racionalidade, define os conhecimentos demandados e cria, via de regra, uma rigidez estratégica que limita o espaço para as contribuições decorrentes dos excedentes cognitivos que poderão não estar relacionados diretamente aos objetivos e metas estabelecidas no plano estratégico. Outra lógica baseada nas culturas da participação, abundância e generosidade é trazida à consideração, na qual as seguintes condições de contorno podem ser observadas: (i) os excedentes cognitivos podem ser identificados como raros, valiosos, não substituíveis, de difícil imitação e decorrentes de longos processos de desenvolvimento, logo, podem distinguir a organização das demais do setor; (ii) os excedentes cognitivos podem induzir novas dinâmicas de funcionamentos para os contextos capacitantes; e, (iii) os contextos capacitantes podem atuar como locais propícios à evidenciação, mobilização e uso desses excedentes. A pesquisa valeu-se, predominantemente, do método, procedimentos e técnicas qualitativas. Foram entrevistados especialistas que atuam como pesquisadores e consultores, com reconhecida projeção nas áreas de Estratégia, Gestão do Conhecimento e Gestão de Pessoas. Os resultados evidenciaram como as organizações lidam com os excedentes cognitivos; o que as organizações poderiam fazer com os excedentes cognitivos; as barreiras que se erguem à evidenciação, mobilização e uso desses excedentes; o que rege a criação dos atuais contextos capacitantes; a existência ou não de espaços de interação construídos intencionalmente pelas organizações; as atitudes dos integrantes das organizações em relação aos excedentes cognitivos; e a percepção dos benefícios que os excedentes cognitivos podem trazer para os stakeholders expressivos da organização.

Optimal two-sided tests for instrumental variables regression with heteroskedastic and autocorrelated errors

This paper considers two-sided tests for the parameter of an endogenous variable in an instrumental variable (IV) model with heteroskedastic and autocorrelated errors. We develop the nite-sample theory of weighted-average power (WAP) tests with normal errors and a known long-run variance. We introduce two weights which are invariant to orthogonal transformations of the instruments; e.g., changing the order in which the instruments appear. While tests using the MM1 weight can be severely biased, optimal tests based on the MM2 weight are naturally two-sided when errors are homoskedastic. We propose two boundary conditions that yield two-sided tests whether errors are homoskedastic or not. The locally unbiased (LU) condition is related to the power around the null hypothesis and is a weaker requirement than unbiasedness. The strongly unbiased (SU) condition is more restrictive than LU, but the associated WAP tests are easier to implement. Several tests are SU in nite samples or asymptotically, including tests robust to weak IV (such as the Anderson-Rubin, score, conditional quasi-likelihood ratio, and I. Andrews' (2015) PI-CLC tests) and two-sided tests which are optimal when the sample size is large and instruments are strong. We refer to the WAP-SU tests based on our weights as MM1-SU and MM2-SU tests. Dropping the restrictive assumptions of normality and known variance, the theory is shown to remain valid at the cost of asymptotic approximations. The MM2-SU test is optimal under the strong IV asymptotics, and outperforms other existing tests under the weak IV asymptotics.