The scale effect in China ? s power grid sector from the perspective of malmquist total factor productivity analysis

China?s power grid sector, which combines transmission and distribution, has grown rapidly after the restructuring reform in 2002. We evaluate the scale effect in the sector by employing a parametric Malmquist index based on a heteroscedastic true fixed-effects stochastic frontier model to estimate technical efficiency and total factor productivity for China?s 30 grid companies from 2002 to 2017. The results show that there exists a scale effect. Most companies exhibit increasing returns to scale, total factor productivity experiences a significant growth driven by scale expansion. Companies with different scales should take differentiated actions to meet the challenges of market-oriented reform.