The present book is a collection of panel data papers, both theoretical and applied. Theoretical topics include methodology papers on panel data probit models, treatment models, error component models with an ARMA process on the time specific effects, asymptotic tests for poolability and their bootstrapped versions, confidence intervals for a doubly heteroskedastic stochastic production frontiers, estimation of semiparametric dynamic panel data models and a review of survey attrition and nonresponse in the European Community Household Panel. Applications include as different topics as e.g. the impact of uncertainty on UK investment, a Tobin-q investment model using US firm data, cost efficiency of Spanish banks, immigrant integration in Canada, the dynamics of individual health in the UK, the relation between inflation and growth among OECD and APEC countries, technical efficiency of cereal farms in England, and employment effects of education for disabled workers in Norway.