我也不太懂,后来在维基上查了一下,大概明白了一点,我理解就是的当一个经济达到帕累托最优的时候是动态有效的,如果通过改变储蓄率能够提高单位有劳动的效用那就说明还处在动态无效的阶段。针对每种模型都有不一样的情况。
1.对于索洛模型来说,当达到黄金律的储蓄率时是动态有效的,其他点都是动态无效的。(这是一句正确的废话)
2.在Ramsey模型中,由于储蓄率是内生的,所以不存在动态有效或无效的问题。
3.对于Diamond模型,模型本身可能就是动态无效的,因为其平衡增长路径上的储蓄率可能超过黄金律的储蓄率。
上面就是维基的主要解释,不过我查了罗默的教材,里面的解释有点不同,主要针对上面的第1点和第2点,书上说由于索洛模型的储蓄率是外生的,实际上无法内生确定平衡增长路径的资本存量水平,因而无法确认他是否等于黄金律水平。书上对Ramsey模型的黄金律水平做了讨论,但是没有直接说明动态有效。
还要在学习一下。
In economics, dynamic efficiency is a situation where it is impossible to make one generation better off without making any other generation worse off. It is closely related to the notion of "golden rule of saving". In general, an economy will fail to be dynamically efficient if the real interest rate is below the growth rate of the economy (sum of the growth rates of population and per capita income).
Dynamic efficiency in the Solow growth model
An economy in the Solow growth model is considered dynamically inefficient, if the savings rate is greater than the Golden Rule savings rate. If the savings rate is greater than the Golden Rule savings rate, a decrease in the savings rate will increase consumption per effective unit of labor. A savings rate higher than the Golden Rule savings rate implies that an economy could be better off today and tomorrow by saving less. [2]
Dynamic efficiency in other models
The Ramsey-Cass-Koopmans model does not have dynamic efficiency problems because agents discount the future at some rate β which is less than 1, and their savings rate is endogenous.
The Diamond growth model is not necessarily dynamically efficient because of the overlapping generation setup; there could be an allocation point, which is better than the competitive equilibrium allocation point, i.e. the equilibrium can be Pareto inefficient. This is because of a finite number of agents. [3]
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