This major drawback led to the development of a more consistent approach that modelled inefficiency effects as an explicit function of certain factors specific to the firm, and all the parameters are estimated in one step using maximum likelihood procedure. Authors in this category include Kumbhakar, Ghosh and McGuckin (1991), Reifschneider and Stevenson (1999), Huang and Liu (1994), and Battese and Coelli (1995), who proposed a stochastic frontier production fuction for panel data. Other authors in recent time include Ajibefun, Battese and Daramola (1996), Coelli and Battese (1996), Battese and Sarfaz (1998), Seyoum et al. (1998), Lyubov and Jensen (1998), Ajibefun and Abdulkadri (1999), Weir and Knight (2000),.
