交通基础设施影响消费的经济增长模型

Cars on the Road: An Economic Growth Model of Road Infrastructure's Effect on Consumption and Economic Growth

交通基础设施对经济发展的影响是多方面的,现有文献多认为交通基础设施通过影响生产行为而对经济发展产生影响。通过观察日益普遍的私家车购买现象,本文发现,交通基础设施不仅影响生产行为,同时也直接影响居民的消费行为。据此,本文构造了一个交通基础设施同时影响生产和消费的增长模型,揭示了道路基础设施通过促进私家车消费,进而改变居民消费结构,最终推动经济增长的机制。为了验证理论命题,本文还构建了中国2000—2012年的省级面板数据并进行了实证研究,发现道路和道路基础设施投资不仅可以直接通过乘数效应促进经济发展,还可以通过提高居民消费中私家车数量及其所占比例(消费效应)间接推动经济增长。

In this paper,we provide a theoretic and empirical framework for evaluating the impacts of road infrastructure on economic growth.We emphasize that road infrastructure directly affects household consumption and economic growth.This consumption channel is mostly ignored in the literature,which focuses on the impacts of transportation infrastructure on supply side factors.Starting with an overlapping generations framework,we develop a simple model featuring road infrastructure and private car purchases.We assume that roads are a public good financed by government tax income.Roads both directly facilitate economic activities and affect household consumption decisions,especially expenditure on private cars.This is because the household utility of using a private automobile is affected by the availability of roads.As a result,public investment in road infrastructure influences the household consumption bundle,further promoting economic growth.This new channel of road infrastructure's contribution to economic growth is called the consumption effect.Our conceptual model leads to five propositions describing the underlying mechanisms through which the government's public investment in road infrastructure affect household consumption and economic growth.(1)As the government invests a higher share of total output in road infrastructure,the equilibrium capital-road ratio decreases,meaning that private capital becomes relatively scarce.(2)The output growth rate is positively associated with the growth rate of road infrastructure;as the share of public investment increases,the economic growth rate first increases and then decreases.(3)The share of household expenditure on private cars increases as road infrastructure improves.(4)The estimated growth rate of the economy is higher when accounting for the new channel through which road infrastructure affects household consumption decisions.(5)As the mileage of roads increases,the benefit from this road consumption channel diminishes.To verify this consumption channel of road infrastructure,we construct a panel dataset of Chinese provinces from 2000 to 2012.We use the total length of all types of roads as the primary indicator of road infrastructure;we also calculate a weighted road length index as an alternative measure using principal component analysis.The main empirical analysis of this paper has two parts.In the first part,we regress provincial GDP on road length and the number of private cars and control for railways,capital stock and labor inputs.We also estimate the relationships between the growth rates of output,roads,and private cars.These baseline results show that both cars and roads are significantly correlated with economic development.In the second part,we empirically verify the underlying mechanisms derived from the theoretic model.We show that the provincial capital-road ratio is significantly negatively correlated with the road investment rate.This indicates that private capital becomes relatively scarce because public investments crowd out private capital.We also explore the link between household consumption and access to road infrastructure as measured by road density.Our results show that the number of private cars and the share of expenditure on private car purchases are significantly higher in provinces with higher road densities after controlling for income and regional fixed effects.Finally,we revisit the impact of roads on economic growth.We show that both road investment and road density demonstrate inverted U shape patterns with growth rate.These findings are consistent with the propositions derived from the model.This paper contributes to the literature by highlighting the consumption effect of infrastructure investments on economic development.Our results have two important policy implications.First,the benefits of public infrastructure investments might be underestimated because the literature ignores this consumption channel,leading to insufficient infrastructure investment.Second,to take advantage of this consumption effect,the design of public infrastructure is very important as the planner must consider the responses of both firms and households.