农业技术发展与经济结构变迁

Agricultural Technology Development and Structural Change

本文发现,工业部门就业与投资率在经济增长过程中呈现的驼峰形变化可以用农业生产技术的转变来解释。从传统农业向现代农业转变需要新的资本投入,转变所释放的剩余劳动力需要积累资本进入其他现代产业,这都增加了对资本品的需求,进而带动工业部门扩张,引发工业化过程。随着农业技术的现代化趋于完成,对资本品的需求渐趋回落,使得工业部门不断收缩,并逐步收敛到长期的广义平衡增长路径上。本文利用一组包括34个国家经济结构变迁过程的数据,对上述推论进行检验并证实:农业部门的变化在工业化过程中对投资率有显著的影响,进而影响了工业部门的就业占比。但是,在去工业化过程中,农业部门的变化将不再影响投资率。

Economic development is always accompanied by structural change in the economy:the agriculture employment share decreases,the service sector employment share increases and the manufacturing employment share exhibits a hump-shaped pattern.To analyze structural change,it is important to consider two aspects:demand and supply side factors.From the demand side,the role of consumption and international trade on structural change are well explored in the literature.However,the role of investment is mostly ignored.We show that the investment rate exhibits another hump-shaped pattern,which can directly affect the manufacturing sector because the production of capital goods is skewed toward manufactured goods.From the supply side,previous studies attribute structural change to different production functions among different sectors.However,structural change can also occur if there is technological change within a sector.Thus,technological change in the agriculture sector(agriculture modernization)can be a key driver of modern economic growth.The goal of this paper is to incorporate these two factors into a general model of structural change.Our theoretical model highlights the importance of agricultural modernization as a central mechanism that triggers the transition from a traditional economy to modern growth.When agriculture relies on traditional technology,which is labor-intensive and does not improve over time,the agriculture sector has to employ a large portion of the labor force to meet the subsistence level of food consumption.Nevertheless,some modern agriculture technology uses reproducible capital as a key input,and its efficiency persistently improves along with other modern sectors at an exogenous rate.After passing a certain threshold,the modern technology becomes superior to the traditional technology and is gradually adopted for agriculture production.This modernization is an endogenous choice by farmers and affects the demand for capital goods(investment)in two ways.First,the adoption of modern technology requires capital inputs,which directly cause investment demand to rise.Second,it releases excess workers to other sectors.These workers have to accumulate capital goods to move and settle down.Both channels increase the demand for physical capital that is produced mostly by the manufacturing sector.As a result,agriculture modernization causes both the investment rate and manufacturing employment to increase(industrialization).When the majority of workers in the traditional agriculture sector have moved into other sectors,agriculture modernization is complete and the investment demand for manufactured goods peaks and begins to shrink,which causes the manufacturing employment share to drop(deindustrialization).Based on the above theoretical model,this paper empirically examines the relationship between structural change and economic growth,using a panel of data from 34 countries from 1950 to 2005.The data source is the 10-sector database from the Groningen Growth and Development Centre.Using fixed effect,random effect and instrument variable models,we confirm two propositions from the theoretical model:1)the stronger the agriculture technology adoption,the higher the investment rate.This relation disappears once manufacturing employment has passed its peak.2)The strength of agriculture technological change has no direct effect on the manufacturing employment share.It has an indirect effect on the manufacturing employment share through the investment rate.This paper contributes to the literature in three ways.First,we provide a unified framework to explain the hump-shaped pattern of manufacturing employment shares by incorporating agriculture modernization,which is a novel explanation for structural change.Second,we emphasize the role of capital accumulation in understanding structural change.We argue that agriculture modernization first affects the investment rate and then affects manufacturing employment.Finally,using numerical simulation and regression analysis,we empirically confirm two implications of our theoretical model.