My panel data have these:
Number of Companies = 10,
Time per Company =9,
Number of Independent Variables = 6
I used First Difference GMM with results as follows:
*1. Number of instruments =71 while the number of cross-sectional units =
9.*
2. The coefficient of the lag of the DV which is used as an independent
variable is less than 1 and statistically significant (p<.001).
3. AR(1) is significant (p<.05)
4. AR(2) is nonsignificant (p>.05)
*5. Sargan Test is significant (p<.05)*
6. Wald Test is significant (p<.01).
Since #1 and #5 are not OK, then First Difference GMM is inappropriate.
I tried the Two-Step Difference and the Systems GMM and all are not OK. Can
you suggest an alternative?