Asymmetric linkages between public-private partnership, environmental innovation, and transport emissions

Figures & data

Table 1. Description of variables.

Sr. No.	Specifications	Variables (Abbreviations)	Source of Data
1	GDP per capita (Constant US$, 2010)	Economic growth (GDP)	World Bank-2020
2	Environmental Innovations (Percentage of total technology innovation)	Environmental Innovations (EI)	OECD-2020
3	Total mid-year Population (Number of Individuals)	Population head count (POP)	World Bank-2020
4	Public and private sector partnership investment in transport (Constant US$)	Public private partnership investment in transport (PPP)	World Bank-2020
5	CO2 emission from transport sector (Metric ton of CO2 emissions per capita)	Carbon dioxide emission from transport sector (TCO)	IEA-2020

Source: Author’s Estimations.

Table 2. Results of descriptive statistics.

Description	TCO	PPP	EI	GDP	GDP^2	POP
Mean	2.129	6.623	0.871	3.029	6.058	9.054
Median	2.061	7.263	0.870	3.017	6.034	9.060
Maximum	2.520	8.399	1.138	3.342	6.683	9.137
Minimum	1.818	1.535	0.503	2.754	5.508	8.947
Std. Dev.	0.223	1.914	0.147	0.176	0.352	0.056
Jarque-Bera	10.676	73.691	3.323	7.374	7.374	7.847
Probability	0.005	0.000	0.190	0.025	0.025	0.020
Observations	116	116	116	116	116	116

Source: Author’s Estimations.

Figure 1. Distribution histograms of data.

Source: Author’s Estimations.

Figure 2. Quantile distribution of data.

Source: Author’s Estimations.

Table 3. Unit root test.

Variable	TCO	PPP	EI	GDP	POP
ADF (Level)	−1.430	−1.936	−1.415	−1.013	−1.920
ADF (Δ)	−2.769***	−3.221***	−3.769**	−2.458***	−3.076***
ZA (Level)	−1.653	−1.794	−2.004	−1.620	−0.867
Year	2009Q3	2002Q1	2007Q2	2011Q3	2016Q1
ZA (Δ)	−3.451***	−4.726***	−4.271**	−3.561***	3.612**
Year	2007Q2	2011Q2	2011Q2	2007Q1	2018Q1

***, ** and * indicate significance at the 1%, 5% and 10% levels, respectively.

Source: Author’s Estimations.

Table 4. Results of quantile autoregressive distributed lag.

Quantiles (τ)	Constant	ECT	Long-run coefficients					Short-run coefficients
	a	ρ	βPPP	βEI	βGDP	βGDP^2	βPOP	φ1 (TCO−1)	ω0 (PPP)	λ0 (EI)	θ0(GDP)	δ0 (GDP^2)	ψ0 (POP)
0.05	0.810	−0.071*	0.066	−0.199	0.535*	−0.267	1.012**	0.427***	−0.073	0.046	0.173	0.010	0.211**
0.10	0.869	−0.069**	0.075	−0.411	0.612**	−0.243	1.020**	0.434***	−0.078	0.041	0.165	0.050	0.189*
0.20	0.679	−0.081**	0.069	0.240	0.879**	−0.282	1.048**	0.452***	−0.045	0.039	0.196	0.041	0.320**
0.30	1.210	−0.064*	−0.083*	0.298	0.766***	−0.273	1.173*	0.578***	−0.059	0.064	0.318**	−0.032	0.456**
0.40	0.925	−0.092**	−0.095**	0.101	0.593*	−0.305	1.203***	0.594***	−0.047	0.079	0.357**	−0.092	0.339*
0.50	1.025	−0.017*	−0.148**	0.098	0.374**	−0.091*	1.276**	0.595***	−0.096	0.034	0.421*	−0.074	0.401**
0.60	1.431	−0.022*	−0.169***	−0.102**	0.310*	−0.110**	1.178**	0.620***	−0.014	−0.042**	0.372*	−0.065	0.142
0.70	0.943	−0.031	−0.165**	−0.127**	0.329*	−0.123***	1.207*	0.648***	−0.095	−0.049**	0.104	−0.043	0.117
0.80	0.482	−0.054*	−0.099*	−0.131***	0.327*	−0.129**	1.102	0.672***	−0.061	−0.056**	0.114	−0.077	0.120**
0.90	0.449	−0.042	−0.010	−0.123***	0.267	−0.210**	1.232**	0.679***	−0.098**	−0.064*	0.098	−0.084	0.134
0.95	0.649	−0.043	−0.040	−0.084**	0.302	−0.229*	1.416**	0.688***	−0.145**	−0.075*	0.077	−0.089	0.128

Note: The table reports the quantile estimation results. The standard errors & t statistics are not reported for the sake of brevity. The significance of coefficients are denoted by astrics, where ***, ** and *indicate significance at the 1%, 5%, and 10% levels, respectively.

Source: Author’s Estimations.

Table 5. Results of the Wald Test for the constancy of parameters.

Variables	Wald-statistics [P-value]
Long-run parameters
ρ	5.371*** [0.000]
βPPP	4.297*** [0.000]
βEI	5.236*** [0.000]
βGDP	7.931*** [0.000]
βGDP2	5.019*** [0.000]
βPOP	5.795*** [0.000]
Short-run parameters
φ1	6.638*** [0.000]
ω0	2.759** [0.049]
λ0	2.329* [0.082]
θ0	2.412*** [0.001]
δ0	2.462* [0.077]
ψ0	0.462 [0.967]

Null hypotheses: Parameters are constant.

Source: Author’s Estimations.

Table 6. Test results of Granger causality in quantile.

Quantiles	[0.05–0.95]	0.05	0.10	0.20	0.30	0.40	0.50	0.60	0.70	0.80	0.90	0.95
ΔPPPt to ΔTCOt	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000
ΔTCOt to ΔPPPt	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000
ΔEIt to ΔTCOt	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000
ΔTCOt to ΔEIt	0.612	0.568	0.663	0.711	0.846	0.976	1.002	1.036	0.992	0.941	0.951	1.041
ΔGDPt to ΔTCOt	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000
ΔTCOt to ΔGDPt	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000
ΔPOPt to ΔTCOt	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000	0.000
ΔTCOt to ΔPOPt	0.569	0.691	0.584	0.642	0.548	0.536	0.620	0.689	0.725	0.614	0.701	0.593

Null hypothesis: No Casual association exist.

Source: Author’s Estimations.