It is well known that when the empirical skewness of the OLS residuals display the opposite sign of what is expected from the stochastic frontier model, maximum likelihood estimation will be equivalent to OLS and no inefficiency will be recovered. A variety of approaches to operate in this...

Typically, the error term in stochastic frontier models is assumed to be positively skewed; however, efficiency scores are biased if this assumption is violated. This paper considers the case in which also negative skewness is allowed in the model. In contrast to other approaches, this skewness is...