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巴罗读史(3):对索洛残差的分析及alwyn模型的本质  

2009-05-02 20:42:48|  分类: 默认分类 |  标签: |举报 |字号 订阅

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三、对索洛残差的分析及Alwyn模型的本质

 

Alwyn's analysis stresses the findings on Solowresiduals, the portion of growth attributed to "technical change"after taking account of quality adjusted growth of labor and capital. Theframework for computing total factor productivity growth is the standard one,based on the production function,

Alwyn的分析,强调了对索洛残差的发现。所谓“索洛残差”,是指:在考虑了对劳动力和资本的质量调整增长之后,归于“技术改变”的增长部分。计算全要素生产率增长的框架,是很标准的教科书,按下面的生产方程来算:

Q = F(K,L,t)              (1)

 

where K and L, the aggregates of capital and labor,are expressed as functions of differentiated subinputs of various kinds. Theresults in Table 6 show TFP growth for Hong Kong averaging 2.9% per year from1961-1966 to 1981-1986, compared with -0.5% per year for Singapore from 1966 to1985. Actually, the TFP growth rate is higher for Singaporein the one interval, 1966-1971 for Hong Kong and 1966-1970 for Singapore, forwhich the investment ratios are similar. For Hong Kong, the TFP growth rate is2.1% per year, whereas for Singapore,it is 2.9% per year. The TFP growth rate for Singapore then plunges when theinvestment ratio soars in the 1970s.

 

其中KL,分别是资本总量和劳动力总量,表示为各色各样的可微“子投入”的函数。论文中的表6,说明了:自1961-19661981-1986年中,每一年的全要素年增长率,香港平均为2.9%,新加坡(1966-1985)却为-0.5%。实际上,在一段时间中,新加坡的全要素增长率却更高一些:1966-1971年是香港高,1966-1970年是新加坡高,在此阶段,投资率是相似的。对于香港来说,全要素增长率为年2.1%;而对新加坡,它是年2.9%。在1970年中,随着新加坡的投资率暴涨,它的全要素增长率,也急速下滑。

 

Within the standard framework, it is hard to see whythe massive investment rates in Singaporewould have led to low TFP growth. The rate of return on capital should fall, asit apparently did, but technical change would not be affected-unless, ofcourse, one shifted away from a model of exogenous technological progress andtoward some other, more substantive model of this progress.

在标准的研究框架里,我们很难知道:为什么新加坡的巨额投资率,会导致全要素增长下降。资本回报率应该是下降的(显然如此),但是,技术改变,却不应该受到影响——当然,除非我们不再是“外生技术进步”模型,而转变为其他的某个更加实质性的、可以解释此种进步的模型。

 

Alwyn sketches such a model that involves theadoption of new tech- nologies and a gradual process of learning about theprocesses that have been adopted. He argues in Table 4 that Singapore hadsuch a rapid rate of structural transformation that it did not benefitsufficiently from productivity improvements because of learning. (I gatherthat, as with the inducements toward high investment, the government's policyof encouraging structural transformation is viewed as simply a mistake?)

Alwyn刻画了这样的一个模型,它包括了对“新技术”的采用,包括了渐近的进步学习过程。在表4中,他指出:新加坡的结构转型速度很快,以至于它不能有效地从学习中获得生产率的提高。(我的推测是:就政府希望的高投资来说,政府鼓励结构转型的政策,是否必然是一个错误决策呢?)

 

Alwyn's model is a particular case of adjustmentcosts related to in- vestment, although the costs arise only when theinvestment is directed to new kinds of products or technologies. Adjustmentscosts are not incurred in this framework simply from a high rate of investment.A further complication is that, in the long run, the new kinds of industries orproducts-once they are learned-allow for greater factor productivity.

Alwyn的模型,是“成本相应于投资进行调整”的一个特例,虽然只在投资被导引向新型产品或技术的时候,成本才会上升。“调整成本”,在这个框架里,并不只是源于“高投资率”。另有一个纠结,那就是:在长期内,新型的产业或新的产品(一旦学到了手之后),就会涉及到更大的要素生产率。

 

I would have liked to see an implementation of thismodel for the TFP analysis. We might then be able to sort out the effects fromadjustment costs caused by high rates of investment from the effects related tostructural transformation. As it stands, the empirical results say more aboutdiminishing returns to capital than they do about technical change.

我很希望看到人们把这个模型应用于全要素分析之中去。这样,我们就能够提炼出“调整成本”的效果了。(因结构转型的效应,而导致的“高投资率下的调整成本”。)正如这里所揭示的,实证的结果,展现得更多的是资本递减收益,而不是技术转变。

 

在这篇论文的结束处,Alwyn批评了简化的内生增长模型(AK模型)。这个模型,讨论了广义资本的积累,而没有涉及到递减收益。他的“递减收益”的证据,就是批评这些模型的基础,虽然因调整成本而导致的短期递减收益,与AK模型中所假设的长期稳定收益,是不冲突的。Alwyn给出的这个模型,实际上,是AK模型的变种。在他的设定中,收益递减趋势,为新思想或新观点的无穷流的发现和采用,而避免。如果人们将这些“新思想”视为某种形式的资本,那么,模型本质上还是假设了“这种资本”上的长期稳定收益。(动态研究,一定比AK模型,在丰富得多,因为在AK模型中,它认为每个部门,都只是有限学习的。)

Toward the end of the paper, Alwyn criticizessimplistic endogenous growth models-AK models-that rely on accumulation of abroad concept of capital without diminishing returns. His evidence on diminishingreturns provides some basis for criticizing these models, although short-rundiminishing returns caused by adjustment costs are consistent with the long-runconstant returns assumed in the AK models. The alternative model that Alwynproposes is actually a variant of the AK models. In his setting, the tendencytoward diminishing returns is avoided by the potential to discover or adapt anunending stream of new products or ideas. If one views these ideas as a form ofcapital, then the model essentially assumes long-run constant returns in thiskind of capital. (The dynamics are considerably richer than those in the AKmodel because of the potential for bounded learning within each sector.) Theeffects of saving behavior and fiscal policies on long-run growth in Alwyn'stype of model seem to be basically similar to those in the primitive AK model.The main differences about tax and subsidy policies involve differentassumptions about market failures, specifically about monopoly power derivedfrom property rights in inventions and about spillover or congestion effectsrelated especially to research and development.

在这篇论文的结束处,Alwyn批评了简化的内生增长模型(AK模型)。这个模型,讨论了广义资本的积累,而没有涉及到递减收益。他的“递减收益”的证据,就是批评这些模型的基础,虽然因调整成本而导致的短期递减收益,与AK模型中所假设的长期稳定收益,是不冲突的。Alwyn给出的这个模型,实际上,是AK模型的变种。在他的设定中,收益递减趋势,为新思想或新观点的无穷流的发现和采用,而避免。如果人们将这些“新思想”视为某种形式的资本,那么,模型本质上还是假设了“这种资本”上的长期稳定收益。(动态研究,一定比AK模型,在丰富得多,因为在AK模型中,它认为每个部门,都只是有限学习的。)在Alwyn式的模型中,储蓄行为与财政政策,对长期增长的效应,与原初的AK模型中的情形,本质上似乎是相似的。在税收和补贴政策上的主要差异,是源于“市场失灵”的不同假设,特别是因发明中的产权效应、溢出效应以及挤出效应(特别与研发问题相关的这些效应)而导致的垄断权力。

 

 

REFERENCES

 

[1]Krause, L.B. (1988). Hong Kong and Singapore:Twins or kissing cousins? Eco- nomic Development and Cultural Change S45-S65.

 

[2]Summers, R., and A. Heston. (1991). The PennWorld Table (Mark 5): An ex- panded set of international comparisons,1950-1988. Quarterly Journal of Eco- nomics 106:327-368.

 

(全文完)

 

 

 

 

 

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