Household size and transport carbon emissions in China: Direct, heterogeneity and mediating effects

Shrinking household sizes presents a significant sustainable challenge by reducing the sharing of means of transportation and increasing individual resource consumption and carbon emissions. Research from the historical literature reveals that larger households generally exhibit lower per capita energy consumption and carbon emissions. However, it remains uncertain how widely these trends extend and their implications for carbon emissions within the expanding transportation industry. This paper employs inter-provincial data from China spanning 2003-2021 to investigate the effects, regional heterogeneity, and mechanisms by which household size influences carbon emissions from the transport sector. The findings show that the expansion of household size in China significantly reduces carbon emissions from transport by 0.2805 %. Households with 2 to 4 members are more effective in achieving transport carbon emission reductions, with an average reduction level of 0.1853 %. Moreover, in terms of geographic factors, reducing transport carbon emissions is more effective in low-density areas than in high-density areas. At the income and carbon emissions level, household size significantly reduces transport carbon emissions in high-income and low-emission regions, and to a lesser extent in low-income and high-emission regions. Additionally, the study revealed that transport consumption expenditure and energy consumption indirectly strengthen the effect of household size on reducing transport carbon emissions. Future sustainable development strategies should focus on regulating household size and promoting moderate household size to decrease personal resource consumption and transportation carbon emissions, and to achieve the objective of sustainable development.