脱钩指数:资源消耗、废物排放与经济增长的定量表达

Decoupling Indicators: Quantitative Relationships between Resource Use, Waste Emission and Economic Growth

本文从资源消耗及废物排放与经济增长的定量关系表达式——IGT方程和IeGTX方程出发,分别导出了资源脱钩指数和排放脱钩指数。根据脱钩指数值,将资源消耗及废物排放与GDP的脱钩程度分为3个等级:绝对脱钩、相对脱钩和未脱钩;在GDP增长和降低两种情况下,脱钩指数与脱钩程度的关系正好相反。由于资源脱钩指数和排放脱钩指数的数学结构相同,只需一个脱钩曲线图就可以判断一个国家或地区某年某种资源消耗或废物排放与GDP的脱钩情况。以中美两国2000年-2007年间的能源消耗和SO2排放为例,阐述了脱钩曲线图的使用方法。在此期间,中美两国的SO2排放脱钩指数略高于各自的能源脱钩指数;中国的能源脱钩指数和SO2排放脱钩指数均低于美国,主要原因是经济增长较快的发展中国家,相对于经济增长较慢的发达国家更难获得较高的脱钩指数。在比较各国间的脱钩程度时,应注意区别对待处于不同发展阶段的国家。

In this paper, a theoretical study on decoupling indicators begins with the derivation of the IGT equation relative to resource use and IeGTX equation concerned with waster emission. Subsequently, a pair of new decoupling indicators was formulated, involving decoupling indicators for resource use （expressed by Dr） and decoupling indicator for waste emission （expressed by De）. Based on the values of these two decoupling indicators, we conceptually divided the decoupling degrees between resource use or waste emission and economic growth into three grades： absolute decoupling, relative decoupling, and non-decoupling. When Dr=0 or De=0, resource use or waste emission increases or decreases synchronously with GDP. And when Dr=1 or De=1, resource use or waste emission remains invariant, regardless of the variation of GDP. Note that in case of economic depression, the relationship between decoupling degrees and decoupling indicators is quite different from that in economic expansion. Since the mathematical structures of the formulas of these two decoupling indicators are identical, only one chart is needed for graphically determining the decoupling indicators for resource use and waste emission for a country in a certain year. When the chart is applied to resource use study, Dr is on the ordinate, and the decreasing rate of resource use per unit GDP （expressed by tr） on each curve. For waste emission study, they will be De and te （the decreasing rate of waste emission per unit GDP） instead. Examples of the decoupling of energy use and SO2 emission in the U.S. and China between 2000 and 2007 were given to illustrate how to use the decoupling chart. In this period, both America’s and China’s decoupling indicators for SO2 emission is slightly higher than their respective decoupling indicators for energy use. Both decoupling indicators for energy use and SO2 emission of China are slightly lower than that of the U.S. This is because developing countries with higher economic growth are generally harder to achieve higher decoupling indicator values compared with developed countries with lower economic growth. Particular attention needs to be paid to different developmental stages at which different countries are when comparing the degrees of decoupling among countries.