Continuous updating gmm estimator who is chuck todd dating
Without loss of generality, we consider one additional explanatory variable beyond the lagged dependent variable, i.e., we restrict .
These results are presented in Table 1, Table 2 and Table 3, respectively, where we compare our subset-continuous-updating estimators (denoted SCUDIF and SCUSYS) to the standard two-step estimators of Arellano and Bond  and Blundell and Bond  (denoted DIF and SYS) from three perspectives: (1) the estimation accuracy, quantified by median absolute errors (MAE), (2) the sampling standard deviations across all simulation repetitions (SD), (3) the Windmeijer  corrected standard errors (SE),4 (4) the size of the two-tailed become twice and four thirds bigger, respectively.
The interpretation gives some insight into why there is less bias associated with this estimator.
The two-step GMM estimators of Arellano and Bond (1991) and Blundell and Bond (1998) for dynamic panel data models have been widely used in empirical work; however, neither of them performs well in small samples with weak instruments.
The DIF GMM estimator was found to be inefficient since it does not make use of all available moment conditions (see Ahn and Schmidt ); it also has very poor finite sample properties in dynamic panel data models with highly persistent series and large variations in the fixed effects relative to the idiosyncratic errors (see Blundell and Bond ) since the instruments in those cases become less informative.
To improve the performance of the DIF GMM estimator, Blundell and Bond  propose taking into consideration extra moment conditions from the level equation that rely on certain restrictions on the initial observations, as suggested by Arellano and Bover .
It is computationally advantageous relative to the continuous-updating estimator in that it replaces a relatively high-dimensional optimization over unbounded intervals by a one-dimensional optimization limited to the stationary domain of the autoregressive parameter.
Since the increase in the length of the panel leads to a quadratic increase in the number of instruments, the two-step DIF and SYS GMM estimators are both biased due to many weak moment conditions; see Newey and Windmeijer .
We show that our subset-continuous-updating method does not alter the asymptotic distribution of the two-step GMM estimators, and it therefore retains consistency.
Our simulation results indicate that the subset-continuous-updating GMM estimators outperform their standard two-step counterparts in finite samples in terms of the estimation accuracy on the autoregressive parameter and the size of the Sargan-Hansen test.
In recent decades, dynamic panel data models with unobserved individual-specific heterogeneity have been widely used to investigate the dynamics of economic activities.
Several estimators have been suggested for estimating the model parameters.