Uncovering the impact of income inequality and population aging on carbon emission efficiency: An empirical analysis of 139 countries

Income inequality and carbon emission efficiency are the primary issues that need to be addressed to achieve UN sustainable development goals. However, research on the relationship between income inequality and carbon emission efficiency has not received enough attention. To more comprehensively understand how income inequality affects carbon emission efficiency, and how aging and economic growth affect the relationship between income inequality and carbon emissions efficiency, fixed effect regression estimation and threshold effect regression estimation approaches are developed based on panel data of 139 countries from 1998 to 2018. The results show that: (i) there is an inhibitory effect of income inequality on the improvement of carbon emission efficiency; (ii) under the influence of aging, there is a U-shaped relationship between income inequality and carbon emission efficiency, that is, income inequality has an inhibitory effect on the improvement of carbon emission efficiency before promoting it; (iii) along with the rapid economic growth, the inhibitory effect of income inequality on carbon emission efficiency increases, that is, there is an inverted U-shaped relationship between income inequality and carbon emission efficiency. Finally, we combine the changes in spatial and temporal distributions to propose corresponding policy recommendations.