Before revision:  Under a strong factor assumption , it is shown that the common component can be consistently estimated but there will be four different convergence rates . Re-estimation of the factors from the imputed data matrix can accelerate convergence.
After revision:  Under a strong factor structure holds for the full panel of data and its sub-blocks , it is shown that the common component can be consistently estimated but there will be four different convergence rates . Re-estimation of the factors from the imputed data matrix can accelerate convergence.