Autoregressive distributed lag models and cointegration

Summary This paper considers cointegration analysis within an autoregressive distributed lag (ADL) framework. First, different reparameterizations and interpretations are reviewed. Then we show that the estimation of a cointegrating vector from an ADL specification is equivalent to that from an error-correction (EC) model. Therefore, asymptotic normality available in the ADL model under exogeneity carries over to the EC estimator. Next, we review cointegration tests based on EC regressions. Special attention is paid to the effect of linear time trends in case of regressions without detrending. Finally, the relevance of our asymptotic results in finite samples is investigated by means of computer experiments. In particular, it turns out that the conditional EC model is superior to the unconditional one. We thank Vladimir Kuzin for excellent research assistance and Surayyo Kabilova for skillful word processing. Moreover, we are grateful to an anonymous referee for clarifying comments.     

Unit root testing

Summary The occurrence of unit roots in economic time series has far reaching consequences for univariate as well as multivariate econometric modelling. Therefore, unit root tests are nowadays the starting point of most empirical time series studies. The oldest and most widely used test is due to Dickey and Fuller (1979). Reviewing this test and variants thereof we focus on the importance of modelling the deterministic component. In particular, we survey the growing literature on tests accounting for structural shifts. Finally, further applied aspects are addressed, for instance, how to get the size correct and obtain good power at the same time. We thank Mu-Chun Wang for producing the figures, and an anonymous referee for comments improving the presentation.     

Jahresbericht 2004/2005

Ohne Zusammenfassung     

Adult sibling relationship questionnaire

This paper presents testing results, as well as the German translation of the “Adult Sibling Relationship Questionnaire” (“ASRQ”), a self-report measure that can be used to raise information on adult sibling relationships. The “ASRQ” consists of 81 items spread over 14 scales. The questionnaire assesses qualitative features of sibling relationships in young adulthood and beyond. The items on the 14 scales are combined to form 3 higher-order factors: “Warmth”, “Conflict” and “Rivalry”. Results of a sample of adults (N=388) confirms that the German version of the “ASRQ” can be very well used as an objective and reliable self-report measure. The analysis of psychometric data confirms early research results on the one hand and point to the necessity of additional research on sibling relations in adulthood on the other hand.     

Why Transition Countries May Specialize in Low-Quality Production

Politicians and economists of transition countries fear a low-quality trap for their economies. We present a model of international trade with two countries and two qualities of goods model where high-quality production exhibits economies of scale and low-quality production does not. Depending on transaction costs, the low-quality good will be produced either in the low-wage economy (i.e., the transition country) only or it will not be traded at all. Regarding the high-quality good, we discuss three potential reasons why transition countries may be trapped in the production of low quality when economies of scale in production prevail: (a) international trade policy (i.e., GATT / WTO); (b) external economies due to quality uncertainty; (c) external economies due to demand effects (big push). All reasons favor incumbents over entrants and thus lead to a low-quality trap for transition economies due to the existence of incumbents located in industrialized countries.     

Optimal Detection of a Change Point in a Poisson Process for Different Observation Schemes

Abstract.  Change point problems are considered where at some unobservable time the intensity of a point process ( T_n ), n ∈  N , has a jump. For a given reward functional we detect the change point optimally for different information schemes. These schemes differ in the available information. We consider three information levels, namely sequential observation of ( T_n ), ex post decision after observing the point process up to a fixed time t * and a combination of both observation schemes. In all of these cases the detection problem is viewed as an optimal stopping problem which can be solved by deriving a semimartingale representation of the gain process and applying tools from filtering theory.     

Checking a Semiparametric Additive Risk Model

McKeague and Sasieni [A partly parametric additive risk model. Biometrika 81 (1994) 501] propose a restriction of Aalen’s additive risk model by the additional hypothesis that some of the covariates have time-independent influence on the intensity of the observed counting process. We introduce goodness-of-fit tests for this semiparametric Aalen model. The asymptotic distribution properties of the test statistics are derived by means of martingale techniques. The tests can be adjusted to detect particular alternatives. As one of the most important alternatives we consider Cox’s proportional hazards model. We present simulation studies and an application to a real data set.