自然垄断与混合所有制改革--基于自然实验与成本函数的分析

Natural Monopoly and Mixed Ownership Reform:Based on the Natural Experiment and Cost Function Analysis Method

混合所有制改革是当前理论探讨的热点。中共十八届三中全会决议已针对城市公用事业等自然垄断领域,提出了改革的纲领。但是,自然垄断领域应该如何推进混合所有制改革仍不明确。具体来说,混合所有制改革应优先在哪些公用事业领域推进,理由是什么,等等。本文使用1998—2008年全国规模以上的公用企业数据,剔除产品价格因素的影响,以成本函数分析方法测算不同的公用事业领域的自然垄断属性及其全要素生产率,并以基于自然实验的三重差分法,对自然垄断、混合所有制改革与企业生产效率之间的关系进行实证检验。结果表明:(1)在统计意义上,混合所有制改革不能显著提升自然垄断环节的企业全要素生产率;(2)混合所有制改革不应该在全国和所有公用事业领域内"一窝蜂"地推进,不区分自然垄断与可竞争程度的改革存在政策效果的不确定性;(3)相对于自然垄断环节,进行混合所有制改革后竞争性环节的企业生产效率得到显著提升,体制改革的"政策红利"更大。因此,混合所有制改革应优先在竞争性环节开展。

With respect to the reform of the natural monopoly of fields such as urban public utility, the literature has mainly focused on whether it is necessary to carry out mixed ownership reform, but few studies have answered practical questions about how the reform should proceed. At the end of 2013, the Central Committee of the Communist Party of China issued a report titled ＂The Decision on Comprehensively Deepening Reform about Some Major Issues＂ in an attempt to develop a fundamental design for the cross-sector reform in mixed ownership and monopoly industries： state-owned capital must retain its control in the industry of natural monopoly, and the primary target for the mixed ownership reform is the competitive links without natural monopoly. However, the type of natural monopoly reform path to be followed is still not clear. Should mixed ownership reform be carried out in natural monopoly industries？ Moreover, in which public industries and links should mixed ownership reform be prioritized？ In response to the above questions and based on a cost function analysis developed by William Baumol and panel data from 1998 to 2008 composed of national urban utilities above a designated size, in this study, we first measured the attributes of natural monopoly at the industry level and the total factor productivity （TFP） at the enterprise level. In particular, we constructed a translog cost function （TCF） with a variable return to scale and used the seemingly unrelated regression （SUR） to estimate the cost functions of the urban utilities in different cities, thus defining the attributes of the city industry natural monopoly by a ＂cost subadditivity＂ standard. In the calculation of the TFP at the enterprise level, we not only derived a TFP estimation equation from the cost function of variable scaled compensations, but also attempted to introduce the semi-parametric estimation model proposed by Olley ＆ Pakes （1996） into the cost function to formulate a new TFP estimation equation. Finally, we sorted a sample consisting of firms that experienced early property rights reform, and empirically tested the relationship between natural monopoly, mixed ownership reform, and the production efficiency of enterprises using the difference-in-differences-in-differences （DDD） method. The main conclusions of this paper were as follows： （ l ） in the natural monopoly link of urban utilities, a mixed ownership reform could not significantly improve the production efficiency of enterprises. （2） The traditional DID model could not verify the remarkable achievements of the mixed ownership reform if the natural monopoly and the competitive link were not distinguished and the implementation of the mixed ownership reform without any distinction contained considerable policy uncertainty. （3） In the competitive link without a natural monopoly, the mixed ownership reform had a significant positive effect on the productivity of the municipal utilities. Compared with that of the natural monopoly, the production efficiency of the competitive link improved significantly after the mixed ownership reform and the ＂ policy dividend＂ of the system reform increased. Therefore, the mixed ownership reform in urban utilities should first be carried out in the competitive links without a natural monopoly. The key to the mixed ownership reform was to determine the natural monopoly property in a specific city and specific public utilities. This work needs to be started with cost data, and thus the accuracy and openness of cost data are crucial. Therefore, in this paper, we suggest that the cost data of the city utilities be made publicly available to government industry management departments; this can be promoted by combining the recent legislative work. A marginal contribution of this paper lies in taking the mixed ownership reform into the framework of natural monopoly theory and specifically distinguishing its heterogeneity effect between monopolistic and competitive links and providing some policy suggestions on the implementation of the mixed ownership reform. This research may inspire and promote the application of natural monopoly theory to the reform of state-owned enterprises.