A simulation estimator for testing the time homogeneity of credit rating transitions

The measurement of credit quality is at the heart of the models designed to assess the reserves and capital needed to support the risks of both individual credits and portfolios of credit instruments. A popular specification for credit-rating transitions is the simple, time-homogeneous Markov model. While the Markov specification cannot really describe processes in the long run, it may be useful for adequately describing short-run changes in portfolio risk. In this specification, the entire stochastic process can be characterized in terms of estimated transition probabilities. However, the simple homogeneous Markovian transition framework is restrictive. We propose a test of the null hypotheses of time-homogeneity that can be performed on the sorts of data often reported. We apply the tests to 4 data sets, on commercial paper, sovereign debt, municipal bonds and S&P-rated Corporates. The results indicate that commercial paper looks Markovian on a 30-day time scale for up to 6 months; sovereign debt also looks Markovian (perhaps due to a small sample size); municipals are well-modeled by the Markov specification for up to 5 years, but could probably benefit from frequent updating of the estimated transition matrix or from more sophisticated modeling, and S&P Corporate ratings are approximately Markov over 3 transitions but not 4.     

协整设定和约束检验及其对我国货币收入速率的实证

本文基于严格的检验，对我国货币M2的长期稳定以及它的收入速率的功能等问题进行协整和弱外生检验，结论表明，我国货币收入速率对于货币需求的长期稳定具有显著作用，而这种长期稳定对货币收入速率又具有显著的调节效应。这一结论隐含了我国货币政策效应可以辅之以货币收入速率予以考察并可以用货币收入速率辅助调节货币需求，而我国利率则是关注参数的弱外生变量，这一结论支持有关扩大利率的浮动范围的利率政策。     

Specification tests in hedonic models

Specification testing can be an effective method for addressing the considerable econometric problems present in hedonic models. In this article, we suggest the use of three different Hausman-type specification tests—tests for the hedonic price equation, each preference equation, and a system of equations—as a way of isolating the sources of misspecification in a hedonic model. Using a national data sample as an example, we illustrate the use of these tests to guide model specification in a simultaneous setting.     

Model specification test with correlated but not cointegrated variables

Many macroeconomic and financial variables show highly persistent and correlated patterns but are not necessarily cointegrated. Recently,  Sun et al. (2011) propose using a semiparametric varying coefficient approach to capture correlations between integrated but non cointegrated variables. Due to the complication arising from the integrated disturbance term and the semiparametric functional form, consistent estimation of such a semiparametric model requires stronger conditions than usually needed for consistent estimation for a linear (spurious) regression model, or a semiparametric varying coefficient model with a stationary disturbance. Therefore, it is important to develop a testing procedure to examine for a given data set, whether linear relationship holds or not, while allowing for the disturbance being an integrated process. In this paper we propose two test statistics for detecting linearity against semiparametric varying coefficient alternative specification. Monte Carlo simulations are used to examine the finite sample performances of the proposed tests.     

三种双指数跳跃扩散模型实证比较研究

本文基于MCMC方法对三种双指数跳跃扩散模型进行了估计,并利用Hong and Li统计量对模型的表现和设定正确性与否给出实证分析,发现广义双指数跳跃扩散模型较接近国内深市的价格模型正确设定,从另一个角度说明深市存在非理性的过度反应行为。当然,结果也显示,模型还需要进一步考虑其他因素。     

A test of non-identifying restrictions and confidence regions for partially identified parameters

We propose an easily implementable test of the validity of a set of theoretical restrictions on the relationship between economic variables, which do not necessarily identify the data generating process. The restrictions can be derived from any model of interactions, allowing censoring and multiple equilibria. When the restrictions are parameterized, the test can be inverted to yield confidence regions for partially identified parameters, thereby complementing other proposals, primarily Chernozhukov et al. [Chernozhukov, V., Hong, H., Tamer, E., 2007. Estimation and confidence regions for parameter sets in econometric models. Econometrica 75, 1243–1285].     

Semiparametric tests of conditional moment restrictions under weak or partial identification

We propose two new semiparametric specification tests which test whether a vector of conditional moment conditions is satisfied for any vector of parameter values θ₀. Unlike most existing tests, our tests are asymptotically valid under weak and/or partial identification and can accommodate discontinuities in the conditional moment functions. Our tests are moreover consistent provided that identification is not too weak. We do not require the availability of a consistent first step estimator. Like Robinson [Robinson, Peter M., 1987. Asymptotically efficient estimation in the presence of heteroskedasticity of unknown form. Econometrica 55, 875–891] and many others in similar problems subsequently, we use k-nearest neighbor (knn) weights instead of kernel weights. The advantage of using knn weights is that local power is invariant to transformations of the instruments and that under strong point identification computation of the test statistic yields an efficient estimator of θ₀ as a byproduct.     

对《井口装置和采油树设备规范》企业“采标”中几个问题的分析

企业在ＡＰＩ Ｓｐｅｃ ６Ａ规范“采标”中,应处理好“采标”的等效性、兼顾性、实用性三个方面的问题。为更好地指导企业的具体“采标”工作,建议应忙抓紧石油井口装置和采油树设备规范行标的修订以及加强全行业“采标”信息的交流工作。     

Hospitality innovation strategies: Robustness analysis of paths to firm performance

Empirical knowledge on the relationship between innovation and firm performance in the hospitality industry is important for theoretical progress and for decision making. Martin-Rios and Ciobanu’s (2019) recent contribution identifies eight different innovation strategies being significantly associated with firm performance including the ambitious strategy of simultaneously innovating products, processes, organizations, and marketing. By replicating the analysis and testing the robustness of the results with a specification curve analysis using the same dataset, we find only three strategies to be robustly associated with firm performance. All three include process innovation as a necessary component: i) a pure backstage-oriented strategy of process and organizational innovation that can be ii) extended with product innovation and iii) a frontstage-oriented strategy, where marketing innovations complement new products and processes. This substantiates the relevance of the process-based view of innovation in services and call for efforts in theorizing about how different configurations of innovation strategies can represent paths to firm performance.     

A Note on Intraday Event Studies

Abstract

We investigate the specification and power of intraday event study test statistics. Mean, market, and matched firm models generate well-specified return results for a range of intervals up to 60?min around the event. These models detect return shocks equivalent to one spread in one-minute interval data and three spreads in longer intervals. Researchers using intraday return event studies can, therefore, be confident in their robustness. Some volume event study approaches have reasonable power but they are not generally well specified, while a matched-firm approach gives the best combination of specification and power for spread event studies.