《中级宏观经济学》第三篇增长理论：超长期中的经济.ppt

单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,*,*,单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,*,第三篇 增长理论：超长期中的经济,第7章,经济增长：资本积累与人口增长,第8章,经济增长：技术、经验和,0,本章内容,索洛模型中的技术进步,增长经验：理论直面现实,促进经济增长的,内生经济增长：内生技术进步的两个简单模型,1,Technological Progress in the Solow Model,The Solow model does not explain technological progress but,instead,takes it as given and shows how it interacts with other,variables in the process of economic growth.,2,前面的索洛增长模型中：,生产技术保持不变,稳态的人均收入是常数,现实世界中上述两点均不成立：,1929-2001：人均实际 GDP 增加了 4.8倍，相对于每年增长 2.2%。,大量的技术进步的例子。,索洛模型中的技术进步,3,技术进步的范例,1970：世界计算机保有量为50,000台。2000：51%的 家庭拥有一台以上计算机。,在过去三十年中，计算机实际价格平均每年下降30%。,1996年生产的普通轿车中包含的计算机处理能力远远超过1969年人类首次登录月球的处理能力。,与二十年前相比，今天的调制解调器要快22倍。,1980年以来，单位GDP中的半导体使用率增加了3500倍。,1981年，因特网联网计算机共有213台；2000年，该数字达到了 60 million。,4,生产函数：,Y=F(K,L,),To incorporate technological progress,Y=F(K,L,E,),E,=,劳动效率,efficiency of labor,L,E,=,有效工人,effective workers,劳动效率的增加类似于劳动力增加，对产出的效果是相同的。,Adding the Efficiency of Labor E,5,Labor-Augmenting Technological Progress,Assume:,labor-augmenting technological progress,能够以外生比率,g,提高劳动效率：,g=,E/E,Technological progress causes,E,to grow at the rate,g,and,L,grows at rate,n,so the number of workers,L,E,is growing at rate,n,+,g,.,Now,the change in the capital stock per worker is:,D,k=i(,d+,n,+,g)k,=sf(k)(,d,+n+g)k,劳动扩张型技术进步,6,符号说明,y=Y/(L E)=单位有效工人的产出,k=K/(L E)=单位有效工人的资本,单位有效工人的生产函数：y=f(k),单位有效工人的储蓄和 ：sy=sf(k),D,k=sf(k)(,d,+n+g)k,7,Capital,per worker,k,k,*,The Steady State,Investment,sf,(,k,),(,d+,n+g),k,sf,(,k,),收支相抵的 (+n+g)k 基本构成 k：资本折旧,n k：新工人提供资本,g k：因技术进步导致的新的有效工人提供资本,k,=,s f,(,k,),(,+,n,+,g,),k,8,Labor-augmenting technological progress at rate,g,affects the Solow growth model in much the same way as did population growth at rate,n.,Now that,k,is defined as the amount of capital per effective worker,increases in the number of effective workers because of technological progress tend to decrease,k,.,In the steady state,investment,sf(k),exactly offsets the reductions in,k,because of depreciation,population growth,and technological progress.,技术进步导致的有效工人数量增加，倾向于减少,k,Important,9,Capital per effective worker is constant in the steady state.Because,y=f(k),output per effective worker is also constant.,But the efficiency of each actual worker is growing at rate,g,.,So,output per worker,(Y/L=y,E),also grows at rate,g,.Total output,Y=y (E L),grows at rate,n+g.,Only technological progress can,explain sustained growth,and persistantly rising standards of living.,The Effects of Technological Progress,10,Steady-state,Growth Rates in the,Solow Model With,Technological Progress,Variable,Symbol,Steady-State,Growth Rate,Capital per effective worker,k=K/(E,L),0,Output per effective worker,y=Y/(E,L)=f(k),0,Output per worker,Y/L=y,E,g,Total output,Y=y,(E,L),n+g,11,Steady-state consumption is maximized if,MPK=,d+,n+g,Or,MPK-,d=,n+g.,资本的净边际产量,MPK-,d,等于总产出增长率,n+g.,引进技术进步修改了 律标准。,The Golden Rule level of capital is now defined as the steady state that maximizes consumption per effective worker.,c*=,f,(k*)-(,d+,n+g,),k*,Golden Rule with technological progress,12,From Growth Theory to Growth Empirics,So far we have introduced technological progress into the,Solow model to explain sustained growth in standards of living.Lets now discuss what happens when theory meets facts.,13,均衡的增长,According to the Solow model,technological progress causes the values of many variables to,rise,together in the steady state,.This property is called,balanced growth,.,均衡的增长,-,多变量同比例增长,索洛增长模型的预测与真实世界相吻合。,Balanced Growth,14,1)In the steady state,output per worker,Y/L,and capital stock per worker,K/L,both grow at rate,g,which is the rate of technological progress.,This is,consistent with U.S.data,in that,g,has been about,2 percent,consistently over the past 50 years.,2)Technological progress also affects factor prices.The,real wage grows at the rate of technological progress,but the,real rental price of capital remains constant,over time.,Again,over the last 50 years,the real wage has increased by,2 percent,and has increased by about,the same as real GDP,.Yet,the real rental price of capital(real capital income divided by the capital stock)has been about the,same,.,15,Convergence,The property of catch-up is called,convergence.,If there is not convergence,countries that start off poor are,likely to remain poor.,The Solow model makes predictions about when,convergence should occur.According to the model,whether two economies will converge depends on why,they differ in the first place(i.e.,savings rates,population growth rates,and human capital accumulation).,趋 同,16,趋 同,索洛模型预测，其它条件不变，“贫困”国家(低,Y/L,且低,K/L,),增长速度应该快于“富裕”国家。,如果为真，那么穷国和富国之间的收入差距将会随时间而缩小，最终，生活标准将会“趋同”,。,在真实世界中，很多贫穷国家增长速度并,不比,富裕国家快。这难道意味着索洛模型失灵了？,17,趋 同,No，,因为“其它条件”并非完全一样的。,在具有相似储蓄率和人口增长率的样本国家中，收入差距每年减少,2%。,在大样本的情况下，如果可以控制储蓄、人口增长、人力资本方面的差异，收入将会按照每年,2%,的速度趋同。,索洛模型的预测实际上是,条件趋同,(conditional convergence),不同国家将会趋近于它们的稳态水平，后者取决于储蓄、人口和教育情况。,该预测和真实世界是吻合的。,18,Factor Accumulation,Versus,Production Efficiency,Differences in income are a result of either:,1)Factors of production such as the quantities of physical and human capital,物质资本或人力资本的差异,2)Efficiency with which economies use their factors of production,生产效率的不同,Workers in a poor country either dont have the tools and skills,or they are not putting their tools and skills to the best use.,19,要素积累和生产效率,研究：,人均（物质或人力）资本较高的国家也趋近于具有较高的生产效率。,解释：,生产效率促进资本积累,资本积累的外部性有利于提高效率,某些未知的第三方变量使得在一些国家中，资本积累和效率比另外一些国家要高。,20,Five Questions,To examine how a nations public policies can influence the level,and growth of the citizens standard of living,we must ask five,questions.,Should our society save more or less?,How can policy influence the rate of saving?,Are there some types of investment that policy should encourage?,What institutions ensure that the economys resources are put,to their best use?,5)How can policy increase the rate of technological progress?,The Solow model provides the theoretical framework within which,we consider these issues.,21,促进增长的,五个 问题：,1）我们储蓄太多还是太少？,2）如何影响储蓄率？,3）是否存在哪些应该特别鼓励的 类型？,4）什么样的制度能保证经济的资源投入其最佳用途？,5）如何提高技术进步率？,22,Key Question,In terms of the Solow model,the central question is whether,the large gap between the rich and poor is explained by,differences in,capital accumulation,or differences in the,production function,.,23,The savings rate determines the steady-state levels of capital and output.One particular saving rate produces the Golden Rule steady state,which maximizes consumption per worker.Lets use the Golden Rule to analyze the U.S.saving rate.,Compare,Marginal product of capital,net of depreciation,(MPK,d,),Growth rate of total output,(n+g),Recall that at the Golden Rule steady state,(MPK,d,)=(n+g),24,储蓄率评估,利用 规则来评估我们的储蓄率和资本存量合意程度。,为此，应该比较(MPK )to (n +g).,如果(MPK )(n +g)，那么，我们处于 规则稳态之下，应该提高 s.,如果(MPK )n+g),If the economy is operating,with more capital than in the,Golden Rule steady state,then,(MPK,d,0.03=n+g,结论：位于 规则稳态之下，如果提高储蓄率，将会促进经济增长，直到达到一个新的稳态为止。此时，人均消费水平将会更高。,储蓄率评估,31,该预测和真实世界是吻合的。,According to the Solow model,technological progress causes the values of many variables to rise together in the steady state.,Capital per effective worker is constant in the steady state.,k =s f(k)(+n+g)k,研究技术进步率的决定因素，而索洛模型视技术进步率是既定的。,n k：新工人提供资本,单位有效工人的储蓄和 ：sy=sf(k),For example,a nations legal tradition is an institution.,Solow Model With,因此，一般认为政府应该鼓励R&D。,2000：51%的 家庭拥有一台以上计算机。,economy,we need to estimate the growth rate of output(n+g)and an estimate of the net marginal product of capital(MPK d).,制造部门，manufacturing firms，生产物品,资本的净边际产量大大超过了增长率，资本存量少于 规则稳态水平。,production function.,现实世界中上述两点均不成立：,K =s Y K,Changing the Rate of Saving,Public saving is the difference between what the government receives in tax revenue minus what it spends,.,When spending revenue,it is a budget deficit,When spending ，那么，收入将不断无休止增长，是“增长的引擎”。,这里，持久收入增长率取决于s，而在索洛模型中，并非如此。,两边除以,K,，,根据,Y,=,A,K,有：,The Basic Model,48,Difference between Solow model and endogenous growth model,In the Solow model,saving leads to growth temporarily,but diminishing returns to capital,eventually,force the economy to approach a,steady state,in which growth depends only on,exogenous technological progress.,By contrast,in this endogenous growth model,saving and investment can lead to persistent growth.,49,资本收益递减吗？,Yes，,-,如果考虑狭义的资本定义,(,工厂和设备,)。,Perhaps not，,-,如果考虑广义的“资本”定义(物质资本，人力资本，知识等,)。,某些经济学家相信，知识表现出,收益递增,的特性。,50,两部门经济,两部门：,制造部门，,manufacturing,firms,，,生产物品,研究部门，,research,universities,，,生产知识，它们可以提高制造部门的劳动效率。,u,=,研究部门劳动力比率(,u,是外生的),制造部门生产函数:,Y,=,F,K,(1-,u,),E L,研究部门生产函数:,E,=,g,(,u,),E,资本积累:,K,=,s Y,K,51,两部门经济,稳态时，制造部门人均产出和生活水准的增长率为：,E/E,=,g,(,u,).,主要变量：,s:,影响收入水平，但是不影响增长率,(,同索洛模型结论一致),u:,同时影响,收入水平和增长率,问题：经济中,u,的增加是否百利无害？,52,真实世界中影响,R&D,的三要素,1.,追逐利润的企业承担了大多数研究。,2.,研究可以为企业带来利润，是因为,新发明受专利保护，在专利失效之前，会带来垄断利润流。,成为新产品市场上的首家企业本身就是一种优势。,3.,创新带来的外部性能降低未来创新的成本。,为了更好理解技术进步，大部分新内生增长理论试图将上述事实融合进模型中去。,53,私人部门的,R&D,水平,知识创造过程中会存在正的外部性，这意味着私人部门进行的,R&D,水平是较低的。,但是，在不同的竞争性公司之间，存在着大量,R&D,的重复投入。,估计：,R&D,带来的社会收益至少每年,40%。,因此，一般认为政府应该鼓励,R&D。,54,Summary,1.技术进步索洛模型的主要结论,人均收入的稳态增长率唯一取决于外生的技术进步率。,在有人口增长和技术进步的索洛模型中，律稳定状态时，资本的净边际产量与总收入稳态增长率相等。,资本的净边际产量大大超过了增长率，资本存量少于 规则稳态水平。,2.经验研究,索洛模型可以解释平衡增长和有条件的趋同。,生活水准的截面国家差异主要是因为资本积累和生产效率的不同。,55,Summary,3.增加储蓄率的方法：,增加公共储蓄（降低预算赤字）,为私人储蓄提供税收刺激,4.生产率减缓和“新经济”,1970s早期：在 和其它主要发达国家，生产率增长率下降。,1990s中期：生产率增长率增加，可能由于I.T.的进步。,5.内生增长理论,研究技术进步率的决定因素，而索洛模型视技术进步率是既定的。,解释R&D引发的知识创造的决策。,56,