Assumptions for Asymptotics o Convergence of moments involving cross section X o Increasing T or Ti assumed fixed Fixed T asymptotics"(see text, p. 196) Time series characteristics are not relevant( may be nonstationary) If T is also growing need to treat as multivariate time series o Ranks of matrices. X must have full column rank. x may not if Ti< k) a Strict exogeneity and dynamics. If Xit contains yi t-1 then xit cannot be strictly exogenous. Xit will be correlated with the unobservables in period t-1.(To be revisited later.) o Empirical characteristics of microeconomic dataAssumptions for Asymptotics  Convergence of moments involving cross section Xi .  N increasing, T or Ti assumed fixed. ◼ “Fixed T asymptotics” (see text, p. 196) ◼ Time series characteristics are not relevant (may be nonstationary) ◼ If T is also growing, need to treat as multivariate time series.  Ranks of matrices. X must have full column rank. (Xi may not, if Ti < K.)  Strict exogeneity and dynamics. If xit contains yi,t-1 then xit cannot be strictly exogenous. Xit will be correlated with the unobservables in period t-1. (To be revisited later.)  Empirical characteristics of microeconomic data