Human capital theory explains the labour productivity level by the workers' level of educational
attainment level (Mincer, 1974; Becker, 1997). Four different effects of human capital on labour
productivity can be found in economic literature: worker, allocative, difusion and research. These
effects are based on the studies of Nelson and Phelps (1966) Welch(1970), Ram (1980),
Pencavel(1991).