Quantile regression 22 Regression analysis 8 Sampling 5 quantile regression 5 Economics 4 CO 2 emission 3 Carbon dioxide 3 Conditional quantiles 3 Finite sample properties 3 Sustainable development 3 Boosted regression tree 2 CO2 emissions 2 COVID-19 2 China 2 Cross validation 2 Decision trees 2 Economic and social effects 2 Economic growths 2 Energy utilization 2 Environmental sustainability 2 Global warming 2 Heterogeneity 2 Instrumental variables 2 Intelligent systems 2 Method of moments 2 Monte Carlo methods 2 Nonparametric quantile regression 2 Nonparametric quantile regressions 2 Ordinary least squares 2 Ordinary least squares (OLS) 2