I am using a panel dataset (N=73; T=9). Dataset Timeframe: 2010-2018
In the GMM estimate on the total dataset, the AR(1) and AR(2) values are fine.
But to investigate the impact of the European crisis, I had to split the data (5 Years during and immediately after the crisis, and the subsequent 4 years). But when GMM is run on the second set of data, (2015-2018), in one of the models, AR(1) and AR(2) values were not generated.
Is the result still usable? What are the potential problems of using this specific result?