In this paper, we devise an alternative environmental policy and design a dynamic environmental tax. The two key features of this approach are: (i) environmental tax is levied on a monopoly firm's emissions intensity (emissions per unit of output) rather than on the firm's total pollution emissions; and (ii) the pollution tax rate is a state variable whose dynamic equation is operationalized with an exponential smoothing process of historical emissions intensity. We compare results from when the monopolist chooses how much effort to expend on developing clean production technology to those when it is chosen by an environmental regulator. Our main results show that: 1) whether under the firm's decision or regulator's adjustment, the saddle-point stability of steady-state equilibrium depends on the discount rate, decay rate of pollutants, and adjustment parameter; 2) the monopolist's output level is higher when the regulator chooses the firm's innovation effort than when the firm does so; 3) when a benevolent regulator chooses the firm's clean technology innovation effort, the level of effort and the resulting level of clean technology are both greater than when the firm makes this choice; 4) the pollution tax and pollution stock are higher under the firm's decision than under the regulator's adjustment.

在本文中，我们设计了一种替代环境政策并设计了一种动态环境税。这种方法的两个关键特征是：（i）环境税是根据垄断企业的排放强度（每单位产出的排放量）而不是企业的总污染排放量征收的；(ii) 污染税率是一个状态变量，其动态方程是用历史排放强度的指数平滑过程来操作的。我们将垄断者选择在开发清洁生产技术上花费多少努力与环境监管机构选择时的结果进行比较。我们的主要结果表明：1）无论是在企业决策还是监管者的调整下，稳态均衡的鞍点稳定性取决于贴现率，污染物衰减率、调节参数；2) 当监管机构选择企业的创新努力时，垄断者的产出水平高于企业选择时的产出水平；3) 当仁慈的监管者选择公司的清洁技术创新努力时，努力水平和由此产生的清洁技术水平都大于公司做出这种选择时；4) 企业决策下的污染税和污染存量高于监管者调整下的污染税和污染存量。努力程度和由此产生的清洁技术水平都比公司做出此选择时更高；4) 企业决策下的污染税和污染存量高于监管者调整下的污染税和污染存量。努力程度和由此产生的清洁技术水平都比公司做出此选择时更高；4) 企业决策下的污染税和污染存量高于监管者调整下的污染税和污染存量。