Special Issue of Econometric Reviews Dependence in Cross-section, Time-series and Panel Data Edited by Badi H. Baltagi and Esfandiar Maasoumi Contents: An Overview of Dependence in Cross-section, Time-series and Panel Data Badi H. Baltagi and Esfandiar Maasoumi Lessons from a Decade of IPS and LLC JoakimWesterlund and Jeorg Breitung Econometric Analysis of High Dimensional VARs Featuring a Dominant Unit Alexander Chudik and M. Hashem Pesaran A Nonparametric Poolability Test for Panel Data Models with Cross Section Dependence Sainan Jin and Liangjun Su A Generalized Spatial Panel Data Model with Random E¤ects Badi H. Baltagi, Peter Egger and Michael Pfa¤ermayr On Two-step Estimation of a Spatial Autoregressive Model with Autoregressive Disturbances and Endogenous Regressors David M. Drukker, Peter Egger and Ingmar R. Prucha Two Stage Least Squares Estimation of Spatial Autoregressive Models with Endogenous Regressors and Many Instruments Xiaodong Liu and Lung-fei Lee Nonparametric Estimation in Large Panels with Cross Sectional Dependence Xiao Huang 1 An Overview of Dependence in Cross-section, Time-series and Panel Data Badi H. Baltagi and Esfandiar Maasoumi In this overview we present a summary of the contents of a collection of latest papers to deal with several aspects of dependence in time-series, cross-section and panels. These papers are collected in this special issue of Econometric Reviews. They include spatial models which usually account for dependence across geographic space as well as social interaction across individuals, see the papers by Baltagi, Egger, and Pfa¤ermayr (2013), Liu and Lee (2013) and Drukker, Egger and Prucha (2013). Also factor models, popular in macroeconomics to account for dependence among countries, see the papers by Chudik and Pesaran (2013) and Huang (2013).1 Additionally, a poolability test for large dimensional semiparametric panel data models with cross-section dependence is proposed by Jin and Su (2013), and a tour de force on what lessons one learns from panel unit root tests and how deceptive inference can be under cross-section dependence is reviewed by Westerlund and Breitung (2013). Westerlund and Breitung (2013) focus on the analysis of panel unit roots and in particular the two in‡uential tests by Levin, Lin and Chu (2002) and Im, Peseran and Shin (2003). These are …rst-generation panel unit roots tests that are appropriate when the cross-sectional units are independent of each other. Westerlund and Breitung emphasize important facts some of them well known and others ignored in this literature. These include the following: (1) The IPS and LLC statistics are standard normally distributed as N ! 1 even if T is …xed; (2) The LLC test can be more powerful than the IPS test; (3) Deterministic components need not be treated as in the Dickey and Fuller approach; (4) Incidental trends reduce the local power of the LLC test; (5) The initial condition may a¤ect the asymptotic properties of the tests. (6) The GMM approach can also be used in the unit root case; (7) Lag augmentation does not remove the e¤ects of serial correlation; (8) The consistency of the LLC test depends on the long-run variance estimator; (9) Cross-section dependence leads to deceptive inference; (10) The IPS and LLC tests fail under cross-unit cointegration; (11) Sequential limits need not imply joint limits. They warn the researcher not to approach the panel unit root testing problem from a too narrow and stylized perspective. Chudik and Pesaran (2013) extend the analysis of in…nite dimensional vector autoregressive (IVAR) models to the case where one of the cross section units in the IVAR model is dominant or pervasive, in the sense that its direct or indirect e¤ects on the rest of the system can lead to strong cross section dependence. An important example in a multi-country analysis is the role of the US in the global economy. The dominant unit in‡uences the rest of the variables in the IVAR model both directly and indirectly, and its e¤ects do not vanish as the dimension 1 See also the papers by Sara…dis and Wansbeek (2011) and Chudik, Pesaran and Tosetti (2011) for important discussion of weak and strong dependence. 2 of the model (N) tends to in…nity. The dominant unit acts as a dynamic factor in the regressions of the non-dominant units and yields an in…nite order distributed lag relationship between the two types of units. Despite this it is shown that the e¤ects of the dominant unit as well as those of the neighborhood units can be consistently estimated by running augmented least squares regressions that include distributed lag functions of the dominant unit and its neighbors (if any). The asymptotic distribution of the estimators is derived and their small sample properties investigated by means of Monte Carlo experiments. Jin and Su (2013) propose a nonparametric poolability test for large dimensional semiparametric panel data models with cross-section dependence. The test requires sieve estimation of the heterogeneous regression relationships under the alternative. They establish the asymptotic normal distributions of their test statistics under both the null hypothesis of poolability and a sequence of Pitman local alternatives. In addition, they prove the consistency of their test and suggest a bootstrap method as an alternative way to obtain the critical values. Using Monte Carlo simulations, they show that their test performs reasonably well in …nite samples. Baltagi, Egger, and Pfa¤ermayr (2013) propose a generalized panel data model with random e¤ects and …rst-order spatially autocorrelated residuals that encompasses two previously suggested speci…cations. The …rst speci…cation assumes that spatial correlation occurs only in the remainder error term, whereas no spatial correlation takes place in the individual e¤ects (see Anselin, 1988, and Baltagi, Song, and Koh, 2003; referred to as the Anselin model). Another speci…cation assumes that the same spatial error process applies to both the individual and remainder error components (see Kapoor, Kelejian, and Prucha, 2007; referred to as the KKP model). The encompassing speci…cation allows the researcher to test for these models as restricted speci…cations using Lagrange Multiplier and Likelihood Ratio tests. Using Monte Carlo experiments, they show that the suggested tests are powerful in testing for these restricted speci…cations even in small and medium sized samples. Drukker, Egger and Prucha (2013) consider a spatial-autoregressive model with autoregressive disturbances, that allows for endogenous regressors. Extending earlier work by Kelejian and Prucha (1998, 1999), they propose a twostep generalized method of moments (GMM) and instrumental variable (IV) estimation approach. They derive the joint limiting distribution of their GMM estimator and the IV estimator for the regression parameters and prove consistency of their GMM estimator for the spatial-autoregressive parameter in the disturbance process. They propose a joint test of zero spatial interactions in the dependent variable, the exogenous variables and the disturbances. Using Monte Carlo experiments, they study the performance of this estimator in small samples. Liu and Lee (2013) consider instrumental variable estimation of spatial autoregressive (SAR) models with endogenous regressors in the presence of many instruments. They derive the asymptotic distribution of the 2SLS estimator when the number of instruments grows with the sample size, and suggest a biascorrection procedure based on the leading-order many-instrument bias. The 3 approximate MSE can be minimized to choose the instruments as in Donald and Newey (2001). Using Monte-Carlo experiments, they …nd that, for the case where some instruments are more important than others, the instrument selection often leads to smaller bias, better precision and more reliable inference. Huang (2013) proposes nonparametric estimation in panel data under cross sectional dependence. The cross sectional dependence has a multifactor structure and the proposed method is an extension of Pesaran’s (2006) procedure using nonparametric estimation. Both the number of cross sectional units (N) and the time dimension of the panel (T) are assumed to be large. Local linear regression is used to …lter the unobserved cross sectional factors and to estimate the nonparametric conditional mean. Monte Carlo simulations show that the proposed method has good …nite sample properties and that the e¢ ciency loss of this nonparametric method decreases as sample size increases. This small collection of papers represent state of art and signi…cant advances in cross-sections, time series and panels with dependence structures. They well represent the major advances that have been made in this area in the last few years. In particular for spatial econometric models analyzing dependence, factor models and IVAR models, nonparametric estimation and testing in panels with dependence, as well as panel unit roots. Badi H. Baltagi Distinguished Professor of Economics CPR Senior Research Associate Center for Policy Research 426 Eggers Hall Syracuse University Syracuse, NY 13244-1020 Email address: bbaltagi@maxwell.syr.edu and Esfandiar Maasoumi Arts & Sciences Distinguished Professor, Department of Economics 1602 Fishburne Drive Emory University, Atlanta, GA 30322 Email address: esfandiar.maasoumi@emory.edu References Anselin, L. (1988). Spatial econometrics: methods and models. Kluwer Academic Publishers, Dordrecht. Baltagi, B.H., P. Egger and M. Pfa¤ermayr (2013),"A Generalized Spatial Panel Data Model with Random E¤ects", Econometric Reviews, Issue 1, Vol 33. Baltagi, B.H., S.H. Song, and W. Koh (2003). Testing panel data models with spatial error correlation. Journal of Econometrics 117, 123-150. 4 Chaudik, A. and M.H. Pesaran (2013),"Econometric Analysis of High Dimensional VARs Featuring a Dominant Unit", Econometric Reviews, Issue 1, Vol 33. Chudik, A., M. H. Pesaran, and E. Tosetti (2011). Weak and strong cross section dependence and estimation of large panels. Econometrics Journal 14, C45–C90. Donald, S. G. and Newey, W. K. (2001). Choosing the number of instruments, Econometrica 69: 1161–1191. Drukker, D.M, P. Egger and I. R. Prucha (2013),"On Two-step Estimation of a Spatial Autoregressive Model with Autoregressive Disturbances and Endogenous Regressors", Econometric Reviews, Issue 1, Vol 33. Huang, X. (2013),"Nonparametric Estimation in Large Panels with Cross Sectional Dependence", Econometric Reviews, Issue 1, Vol 33. Im, K. S., M. H. Peseran and Y. Shin (2003). Testing for Unit Roots in Heterogeneous Panels. Journal of Econometrics 115, 53–74. Jin, S. and L. Su (2013),"A Nonparametric Poolability Test for Panel Data Models with Cross Section Dependence", Economertric Reviews, Issue 1, Vol 33. Kapoor, M., H.H. Kelejian, and I.R. Prucha (2007). Panel data models with spatially correlated error components. Journal of Econometrics 140, 97-130. Kelejian, H.H. and Prucha, I.R. (1998). A Generalized Spatial Two-Stage Least Squares Procedure for Estimating a Spatial Autoregressive Model with Autoregressive Disturbances. Journal of Real Estate Finance and Economics 17, 99-121. Kelejian, H.H. and Prucha, I.R. (1999). A Generalized Moments Estimator for the Autoregressive Parameter in a Spatial Model. International Economic Review 40, 509-533. Levin, A., C. Lin, and C.-J. Chu (2002). Unit Root Tests in Panel Data: Asymptotic and Finite-sample Properties. Journal of Econometrics 108, 1–24. Liu, X. and L-F. Lee (2013),"Two Stage Least Squares Estimation of Spatial Autoregressive Models with Endogenous Regressors and Many Instruments", Econometric Reviews, Issue 1, Vol 33. Pesaran, M. H. (2006). Estimation and inference in large heterogeneous panels with a multifactor error structure. Econometrica 74: 967-1012. Pesaran, M. H. and E. Tosetti (2011). Large panels with common factors and spatial correlations. Journal of Econometrics 161, 182–202. Sara…dis, V. and T. Wansbeek (2012). Cross-sectional dependence in panel data analysis, forthcoming in Econometric Reviews (to update later). Westerlund, J. and J. Breitung (2013),"Lessons from a Decade of IPS and LLC", Econometric Reviews, Issue 1, Vol 33. 5