In the second step, in order to estimate the regressions related to the profitability determinants, we use dynamic panel estimators, namely the GMM (1991), GMM system (1998) and LSDVC (2005) estimators.
The following Table 6 presents the regressions referring to the relationships between determinants and profitability in young SMEs and old SMEs, using the GMM (1991), GMM system (1998) and LSDVC (2005) (9) estimators.
The results obtained with the LSDVC (2005) estimator corroborate, in general, those obtained with the GMM system (1998), regarding the sign, magnitude and statistically significance of the estimated parameters.
Based on the various results obtained, we will consider the empirical evidence from using the GMM system (1998) and LSDVC (2005) estimators as our reference for interpreting the results.
Whether using the GMM system (1998) estimator or the LSDVC (2005) estimator, we reject the null hypothesis of equality of estimated parameters for the relationships between the determinants considered and profitability in young and old SMEs.