While previous study has confirmed significant correlation between infrastructure construction and air quality, little is known about the nature of the relationship. In this paper, we intend to fill this gap by using the Panel Smooth Transition Regression (PSTR) model to discuss the nonlinear relationship between transportation infrastructure construction and air quality. The panel data includes 280 cities in China for the period 2000-2017. We find that the transportation infrastructure investment is positively correlated to the air quality when the GDP per capita is below RMB 7151 or the number of motor vehicle population per capita is below 37 (vehicles per 10,000 persons) where the model is in the lower regime, and that the transportation infrastructure investment is negatively correlated to the air quality when the GDP per capita is greater than RMB 7151 or the number of motor vehicle population per capita is larger than 37 (vehicles per 10,000 persons) where the model is in the upper regime. The empirical results of the three sub-samples, including eastern, western and central regions, are similar to that of the national level. Furthermore, increasing transportation infrastructure investment is conducive to improving air quality. Urban bus services, green area, population density, wind speed and rainfall are also conducive to reducing air pollution, but the role of environmental regulation is not significant. After adding the instrumental variable (urban built-up area), the conclusions are further supported. Finally, relevant policy recommendations for reducing air pollution are proposed based on the empirical results.

Using an unbalanced panel data consisting of deaths from natural disasters and fivefactors of financial risks in 136 countries, this paper analyzes the effect of naturaldisasters on different financial risks. The conclusions are as follows: (1) naturaldisasters lead to financial crisis by reducing GDP and trade and increasing domesticand foreign debt; (2) the effects of natural disasters on financial risks are dynamic andlong term, with the effect weakening with time; and (3) the negative effects of naturaldisasters on financial risks in high-income and OECD countries are smaller than thoseof low-income and non-OECD countries.

The Internet usage in rural areas has already greatly improved the quality of rural life and income level of rural residents in China. However, there is a lack of discussion on the impact of Internet use on the income of returning migrant workers. This paper investigates the impact of Internet use on the income of returning migrant workers, its potential channel, as well as family income categories and consumption categories as the extension by using the data of CLDS from 2014 to 2018. We find that, firstly, Internet use can significantly improve the total income level of returnees, and this conclusion is not changed after considering the endogeneity problem and do several other robust checks. Secondly, the accumulation of social capital, the accumulation of material capital and the improvement of entrepreneurial probability are the three main channels for the Internet to improve the income of returnees. Heterogeneity analyses show that compared with western regions, low-income groups and religious believers, Internet use in central and eastern regions, high-income groups and non-religious returnees has a stronger impact in promoting income. Finally, the extended analyses show that the use of the Internet mainly improves the non-agricultural income of returning households, and increases family improved consumption as a result. This paper indicates that the government should further strengthen the policy of Internet use of returnees to help them improve their income level and quality of life.