Table 2. Summary review of literature invalidating EKC hypothesis.

Study	Dataset	Period	Econometric technique	Outcome
[73]	Chinese provincial level	1985–2015	VECM	EKC at aggregate-level for SO2 EKC may not exist at the provincial-level for SO2
[74]	100 states	1960–1996	Nonparametric panel model with individual effects	Upward sloping curve for CO2
[44]	Turkey	1968–2003 1992–2001	Johansen technique, Feasible Generalized Least Squares	Monotonically increasing curve for CO2 N-shaped for SO2 and PM10
[45]	Tunisia	1961–2004	Johansen technique, Granger causality	Monotonically increasing curve for CO2
[35]	Korea	1990–2005	Fixed-effects, Random-effects, Random coefficient regressions	Potential N-shaped curve for SO2 Dominant U-shaped curve for CO A region-specific U-shaped curve for NO2
[75]	8 states	1970–2010	ARDL	Inverted U-shaped curve for CO2 in Japan and South Korea N-shaped curve for Brazil, China, Egypt, Mexico, Nigeria, and South Africa
[76]	25 Sub-Saharan Africa states	1996–2010	Ordinary Least Squares, Difference GMM, System GMM, Least Square Dummy Variable Corrector	Monotonically increasing curve for CO2
[77]	189 states	1990–2012	Fixed-effects and Random-effects panel regressions, Dynamic panel regressions, Heterogeneous panel regressions	Linearly increasing curve for CO2
[78]	China	1997–2012	Non-spatial panel models and spatial Durbin model	Inverted N-shaped curve for CO2
[51]	17 OECD states	1990–2012	Fixed-effect panel regressions	N-shaped curve for per capita GHG emissions
[79]	India, China	1971–2012	ARDL	N-shaped curve for CO2
[80]	Saudi Arabia	1970–2014	ARDL	GDP growth and CO2 emissions are positively and linearly associated

Source: Authors’ compilation based on literature review.