不确定性与中国出口增长

Uncertainty and China's Export Growth

本文针对近期中国出口波动幅度增加以及国际金融危机以来贸易出现"过度反应"的事实,利用中国对59个主要贸易伙伴的出口数据以及出口目标国的宏观经济变量,研究了外部不确定性与中国出口波动的数量关系和因果关系。研究发现:(1)从数量关系上来看,不确定性和外部冲击会对中国出口产生负面影响,而且这个影响的量级在短期内要远远大于传统上所考虑的供给、需求以及汇率因素所产生的影响;(2)使用灾难数据作为工具变量的两阶段最小二乘法估计表明,不确定性与中国出口增长存在着稳定的负向因果关系;(3)不确定性冲击对中国出口的影响具有异质性特征。这些发现意味着营造一个稳定有序的经济环境应该成为政策制定者的首要之选,而企业要着力对未来的需求形成科学有效的预判,以期对冲不确定性对出口增长的影响。

The recent global economic crisis saw a sharp decline in output. However, the accompanying declines in Chinese export and world trade volume were sharper and almost twice as big. The failure of traditional models to account for these developments suggests that the behavior of trade in exceptional circumstances may still be poorly understood. Traditional trade theory intrinsically fails to explain the quantitative relationship between economic uncertainty and trade, as the classical trade model is based on full information and sufficient rational assumptions. Popular analytical tools used to explain bilateral trade flows, such as the gravity equation, entirely fail to consider the effect of uncertainty. To date, the analysis of the effects of uncertainty on trade has remained largely confined to exchange rate volatility. Studies have generally found that the effect of exchange rate volatility on aggregate trade flows is ＂fairly small and by no means robust＂. Yet, a crisis of confidence and an increase of uncertainty may easily curtail international trade, as investment and consumption decisions are put on hold （Taglioni ＆ Zavacka, 2012）. Knight （ 1921 ） defines uncertainty as peoples＇ inability to forecast the likelihood of events happening. Uncertainty is a broad concept that can refer to fluctuations in macroeconomic variables （such as GDP, total consumption, and investment） , or fluctuations in microeconomic variables （such as corporate returns, war, climate change, and economic events）. Macro and micro uncertainties have typical inverse cycles. Uncertainty increases in times of economic recession and decreases as economy booms （Baker ＆ Bloom, 2013）. Short-term uncertainty leads to a longer period of economic activity decline that lasts for some time. This phenomenon is referred to as the ＂uncertainty trap＂. Against both the recent increase of China＇s export volatility and the overreaction of trade to exogenous shocks during crises, this study investigates the statistical and causal relationship between uncertainty and China＇s export volatility. We construct cross-country panel data on stock market volatility as proxies for the second moments of business conditions. The study arrives at the following findings. （1） From a quantitative viewpoint, uncertainty and external shocks have a negative effect on China＇s exports, and the magnitude of the effect in the short term is much larger than the traditional considerations of supply, demand, and exchange rate. （2） The two-stage least squares estimations using disaster data as instrumental variables show a stable negative causal relationship between uncertainty and China＇s export growth. （3） The effects of uncertainty on China＇s exports have heterogeneous characteristics, such as different countries, export scales, and periods. These findings mean that creating a stable and orderly economic environment should be the primary choice for policymakers, and that companies should focus on scientific and effective predictions of future demand to limit the effects of uncertainty on export growth. This study enriches and expands the current research in the following ways. First, it explains the volatility of China＇s total exports in relation to external uncertainty by extending specific economic variables to general confidence or psychological shocks. This differs from supply-demand and other practical economic theories used to interpret the paradigm of China＇s export growth. Second, the VAR model quantitatively presents the effects of the intensity and duration of uncertainty on Chinese exports, and compares the effects of uncertainty, exchange rate, and supply and demand on those exports. Third, this study helps us to better understand the potential negative effects of globalization and thus identify external risks to China＇s exports. Finally, this study uses natural disasters, terrorist attacks, political shocks, and other exogenous shocks as instrumental variables of uncertainty to solve potential endogenous problems.