Water–Energy–Milk Nexus: Empirical Evidence from Saudi Arabia
Abstract
:1. Introduction
2. Literature Review
2.1. Milk–Water Nexus
2.2. Milk–Energy Nexus
2.3. Milk–Water–Energy Nexus
3. Data and Methods
3.1. Data
3.2. Approaches
3.2.1. Unit Root and Cointegration Tests
3.2.2. VAR Model
3.2.3. Granger Causality Test
3.2.4. Impulse Response Functions and Variance Decompositions
4. Results and Discussion
4.1. Unit Root and Cointegration Results
4.2. VAR Results
4.3. Granger Causality Approach Results
4.4. Forecast Error Variance Decomposition Results
4.5. Impulse Response Function Results
4.6. Robustness Check: FMOLS Estimator Results
5. Conclusions and Policy Implications
Author Contributions
Funding
Data Availability Statement
Conflicts of Interest
Appendix A
Variable | Model (A) Intercept * | Model (B) Trend ** | Model (C) Trend and Intercept *** | |||
---|---|---|---|---|---|---|
t-Stat | SBD | t-Stat | SBD | t-Stat | SBD | |
LnTMP | −5.599 | 2015 | −5.018 | 2009 | −5.741 | 2015 |
lnWSA | −6.035 | 2007 | −5.048 | 2011 | −6.034 | 2007 |
LnWSI | −4.625 | 2015 | 4.282 | 2008 | −5.450 | 2018 |
LnREC | −5.631 | 2016 | −4.658 | 2017 | −7.947 | 2016 |
Appendix B
Trace Statistics Test | Conclusion | ||||||
---|---|---|---|---|---|---|---|
Hypothesized No. of CE(s) | Params | LL | Eigenvalue | Trace Statistic | Critical Value (1%) | p-Value | |
r = 0 | 20 | 142.929 | 50.057 | 54.682 | 0.031 | H0 accepted | |
r ≥ 1 | 27 | 155.791 | 0.7237 | 24.333 | 35.458 | 0.187 | H0 accepted |
r ≥ 2 | 32 | 164.002 | 0.5601 | 7.909 | 19.937 | 0.475 | H0 accepted |
r ≥ 3 | 35 | 167.957 | 0.309 | 0.490 | 6.635 | 0.484 | H0 accepted |
r ≥ 4 | 36 | 167.957 | 0.024217 | ||||
Maximum Eigenvalue test | |||||||
Hypothesized No. of CE(s) | Params | LL | Eigenvalue | Max-Eigen statistic | Critical Value (1%) | p-Value | |
r ≥ 0 | 20 | 142.929 | 25.724 | 32.715 | 0.085 | H0 accepted | |
r ≥ 1 | 27 | 155.791 | 0.724 | 16.424 | 25.861 | 0.201 | H0 accepted |
r ≥ 2 | 32 | 164.003 | 0.560 | 7.419 | 18.520 | 0.441 | H0 accepted |
r ≥ 3 | 35 | 167.957 | 0.310 | 0.490 | 6.635 | 0.484 | H0 accepted |
r ≥ 4 | 36 | 167.957 | 0.024 | ||||
Information criteria | |||||||
Hypothesized No. of CE(s) | Params | LL | Eigenvalue | SBIC | HQIC | AIC | |
r ≥ 0 | 20 | 142.929 | −11.297 | −12.098 | −12.293 | Not selected | |
r ≥ 1 | 27 | 155.791 | 0.724 | 11.535 | −12.617 | −12.879 | Not selected |
r ≥ 2 | 32 | 164.003 | 0.560 | −11.607 * | −12.889 | −13.200 | Selected |
r ≥ 3 | 35 | 167.957 | 0.310 | −11.529 | −12.931 * | 13.271 | Selected |
r ≥ 4 | 36 | 167.957 | 0.024 |
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1. Correlation Matrix | ||||
Variable | TMP | WSA | WSI | REC |
TMP | 1.00 | |||
WSA | 0.29 (0.19) | 1.00 | ||
WSI | 0.93 *** (0.00) | 0.51 *** (0.01) | 1.00 | |
REC | −0.06 (0.78) | −0.006 (0.98) | −0.15 (0.51) | 1.00 |
2. Descriptive Statistics | ||||
Mean | 1,873,405.00 | 776.70 | 33.51 | 232.94 |
Std. dev. | 645,574.60 | 27.99 | 12.08 | 35.73 |
Min | 952,500.00 | 719.17 | 11.35 | 181.71 |
Max | 2,916,104.00 | 830.15 | 52.49 | 285.33 |
3. Normality Tests: | ||||
A. Skewness and kurtosis tests | ||||
Statistics test | Pr (skewness) | Pr (kurtosis) | Joint test | |
chi2(2) | Prob > chi2 | |||
TMP | 0.864 | 0.017 | 5.71 | 0.058 |
WSA | 0.648 | 0.788 | 0.28 | 0.869 |
WSI | 0.890 | 0.695 | 0.17 | 0.917 |
REC | 0.611 | 0.035 | 4.73 | 0.094 |
B. Shapiro–Wilk W test | ||||
Statistics test | W | V | Z | Prob > z |
TMP | 0.922 | 1.982 | 1.387 | 0.083 |
WSA | 0.971 | 0.732 | −0.632 | 0.736 |
WSI | 0.943 | 1.441 | 0.740 | 0.229 |
REC | 0.908 | 2.340 | 1.724 | 0.042 |
Predictor Variable | Response Variable: Equations | |||
---|---|---|---|---|
LnTMP: Equation (4) | LnWSA: Equation (5) | LnWSI: Equation (6) | LnREC: Equation (7) | |
LnTMP (-1) | 0.115 [0.142] (0.809) | −0.044 [0.093] (−0.474) | −0.128 [0.108] (−1.185) | −0.062 [0.324] (−0.190) |
LnTMP (-2) | 0.213 [0.141] (1.509) | 0.037 [0.093] (0.396) | 0.151 [0.107] (1.407) | −0.212 [0.322] (−0.660) |
LnTMP (-3) | 0.184 [0.128] (1.440) | −0.179 [0.084] (−2.133) ** | 0.363 [0.097] (3.740) *** | −0.344 [0.291] (−1.183) |
LnWSA (-1) | −0.164 [0.340] (−0.483) | 0.567 [0.222] (2.551) *** | 0.088 [0.257] (0.343) | −3.023 [0.772] (−3.917) *** |
LnWSA (-2) | −1.610 [0.628] (−2.565) *** | −0.042 [0.411] (−0.103) | 0.282 [0.476] (0.592) | 2.000 [1.427] (1.401) |
LnWSA (-3) | 1.516 [0.427] (3.549) *** | −0.572 [0.280] (−2.045) ** | 0.472 [0.324] (1.458) | −0.858 [0.971] (−0.884) |
LnWSI (-1) | 0.389 [0.157] (2.483) ** | 0.021 [0.103] (0.208) | 0.355 [0.119] (2.986) *** | 0.244 [0.356] (0.685) |
LnWSI (-2) | 0.313 [0.156] (2.012) ** | 0.100 [0.102] (0.978) | 0.048 [0.118] (0.409) | 0.018 [0.354] (0.051) |
LnWSI (-3) | −0.185 [0.139] (−1.327) | 0.055 [0.091] (0.597) | −0.006 [0.106] (−0.058) | 0.237 [0.317] (0.747) |
lnREC (-1) | −0.220 [0.122] (−1.812) * | −0.119 [0.080] (−1.498) | 0.006 [0.092] (0.067) | 1.016 [0.276] (3.677) *** |
lnREC (-2) | 0.790 [0.178] (4.429) *** | −0.026 [0.117] (−0.223) | −0.573 [0.135] (−4.243) *** | −0.511 [0.405] (−1.261) |
lnREC (-3) | −0.460 [0.097] (−4.739) *** | 0.137 [0.064] (2.148) ** | 0.308 [0.074] (4.187) *** | 0.380 [0.221] (1.718) * |
Constants | 6.418 [3.231] (1.986) ** | 9.085 [2.115] (4.296) *** | −7.527 [2.449] (−3.074) *** | 20.301 [7.343] (2.765) *** |
PARMS | 13 | 13 | 13 | 13 |
RMSE | 0.035 | 0.023 | 0.027 | 0.080 |
R-sq | 0.996 | 0.790 | 0.997 | 0.913 |
X2 | 4504.641 *** | 71.424 *** | 5996.207 *** | 200.198 *** |
Lag | LogL | LR | FPE | AIC | SC | HQ |
---|---|---|---|---|---|---|
0 | 71.393 | NA | 9.76 × 10−9 | −7.094 | −6.895 | −7.060 |
1 | 145.885 | 109.778 * | 2.17 × 10−11 | −13.251 | −12.257 | −13.083 |
2 | 163.335 | 18.368 | 2.47 × 10−11 | −13.404 | −11.614 | −13.101 |
3 | 201.290 | 23.972 | 5.97 × 10−12 * | −15.715 * | −13.130 * | −15.277 * |
* Root | Modulus |
---|---|
0.987 | 0.987 |
0.777 + 0.418 i | 0.882 |
0.777 −0.418 i | 0.882 |
0.449 +0.759 i | 0.882 |
0.449–0.759 i | 0.882 |
−0.326 + 0.764 i | 0.831 |
−0.326–0.764 i | 0.831 |
0.741 | 0.741 |
−0.614 | 0.614 |
−0.516 + 0.139 i | 0.534 |
−0.516–0.139 i | 0.053 |
0.173 | 0.173 |
Lagrange Multiplier Test | |||
---|---|---|---|
Lag | X2 | P > X2 | Decision |
1 | 12.583 | 0.703 | H0 accepted |
2 | 20.865 | 0.184 | H0 accepted |
3 | 16.322 | 0.431 | H0 accepted |
4 | 18.978 | 0.270 | H0 accepted |
Predict error, residual | Mean (Std. dev) | [Min] [Max] | |
Value | −1.08 × 10−10 (0.039) | [−0.081] [0.079] | Accuracy in the model’s predictions |
Equation: LnTMP | |||
---|---|---|---|
Excluded | Chi2 | p-Value | Causality, Direction |
LnWSA | 21.876 | 0.000 *** | WSA ←→TMP. bidirectional |
LnWSI | 23.235 | 0.000 *** | WSI ←→ TMP, bidirectional |
LnREC | 46.222 | 0.000 *** | REC←→ TMP, bidirectional |
All | 121.55 | 0.000 *** | Causality |
Equation: LnWSA | |||
Excluded | Chi2 | p-value | Causality, direction |
LnTMP | 9.6907 | 0.021 ** | TMP ←→ WSA, bidirectional |
LnWSI | 7.6562 | 0.054 * | WSI ←→WSA, bidirectional |
LnREC | 17.668 | 0.001 *** | REC ←→ WSA, bidirectional |
All | 24.454 | 0.004 *** | Causality |
Equation: LnWSI | |||
Excluded | Chi2 | p-value | Causality, direction |
LnTMP | 39.863 | 0.000 *** | TMP ←→ WSI, bidirectional |
LnWSA | 12.841 | 0.005 *** | WSA←→ WSI, bidirectional |
LnREC | 89.934 | 0.000 *** | REC→ WSI, unidirectional |
All | 236.05 | 0.000 *** | Causality |
Equation: LnREC | |||
Excluded | Chi2 | p-value | Causality, direction |
LnTMP | 8.0037 | 0.046 * | TMP ←→REC, bidirectional |
LnWSA | 18.66 | 0.000 *** | WSA←→ REC, bidirectional |
LnWSI | 4.908 | 0.179 | No causality |
All | 42.218 | 0.000 *** | Causality |
Horizons | Variance Decomposition of LnTMP | Variance Decomposition of LnWSA | ||||||
---|---|---|---|---|---|---|---|---|
TMP | WSA | WSI | REC | TMP | WSA | WSI | REC | |
1 | 100.000 | 0.000 | 0.000 | 0.000 | 0.701 | 99.300 | 0.000 | 0.000 |
2 | 85.921 | 1.775 | 1.088 | 11.216 | 2.007 | 89.840 | 0.169 | 7.985 |
3 | 46.518 | 2.872 | 7.245 | 43.365 | 8.135 | 69.488 | 0.265 | 22.112 |
4 | 40.650 | 11.481 | 7.135 | 40.734 | 7.462 | 63.726 | 0.249 | 28.563 |
5 | 43.004 | 11.135 | 6.609 | 39.252 | 7.389 | 63.791 | 0.247 | 28.574 |
6 | 38.167 | 23.914 | 5.481 | 32.438 | 7.250 | 63.010 | 0.602 | 29.138 |
7 | 38.808 | 28.140 | 4.415 | 28.637 | 7.340 | 62.948 | 0.682 | 29.031 |
8 | 38.095 | 25.549 | 3.539 | 32.817 | 7.258 | 62.383 | 0.675 | 29.684 |
9 | 37.254 | 25.466 | 3.330 | 33.950 | 7.149 | 62.122 | 0.689 | 30.040 |
10 | 37.706 | 24.075 | 3.151 | 35.068 | 7.383 | 61.220 | 0.772 | 30.624 |
Horizons | Variance Decomposition of LnWSI | Variance Decomposition of LnREC | ||||||
TMP | WSA | WSI | REC | TMP | WSA | WSI | REC | |
1 | 5.542 | 50.771 | 43.687 | 0.000 | 13.002 | 26.082 | 2.276 | 58.641 |
2 | 5.323 | 52.801 | 41.859 | 0.017 | 17.072 | 17.862 | 3.397 | 61.670 |
3 | 18.127 | 22.781 | 14.635 | 44.457 | 19.546 | 15.388 | 3.797 | 61.269 |
4 | 27.541 | 26.568 | 6.786 | 39.104 | 26.255 | 12.006 | 3.490 | 58.249 |
5 | 28.739 | 25.045 | 5.011 | 41.205 | 26.042 | 10.279 | 3.158 | 60.522 |
6 | 32.806 | 23.162 | 4.090 | 39.942 | 26.191 | 10.519 | 3.127 | 60.163 |
7 | 32.211 | 21.956 | 3.781 | 42.051 | 25.271 | 14.262 | 2.972 | 57.495 |
8 | 32.386 | 22.284 | 3.820 | 41.509 | 25.393 | 15.165 | 2.943 | 56.499 |
9 | 32.569 | 23.126 | 3.693 | 40.612 | 25.721 | 15.094 | 2.934 | 56.252 |
10 | 34.268 | 22.343 | 3.590 | 39.799 | 26.334 | 15.090 | 2.904 | 55.672 |
Predictor Variable | Coefficient (β) | Newey–West Std. Error | t-Statistic |
---|---|---|---|
LnWSA | −2.016 | 0.5180 | −3.891 *** |
LnWSI | 0.032 | 0.002 | 20.564 *** |
LnREC | 0.002 | 0.000 | 4.994 *** |
C | 26.194 | 3.437 | 7.621 *** |
R-squared | 0.927 | ||
S.E. of regression | 0.102 | ||
S.D. dependent variance | 0.349 | ||
Long-run variance | 0.005 | ||
Sum squared residues | 0.178 |
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Elzaki, R.M.; Al-Mahish, M.; Alzahrani, F. Water–Energy–Milk Nexus: Empirical Evidence from Saudi Arabia. Water 2024, 16, 1538. https://doi.org/10.3390/w16111538
Elzaki RM, Al-Mahish M, Alzahrani F. Water–Energy–Milk Nexus: Empirical Evidence from Saudi Arabia. Water. 2024; 16(11):1538. https://doi.org/10.3390/w16111538
Chicago/Turabian StyleElzaki, Raga M., Mohammed Al-Mahish, and Fahad Alzahrani. 2024. "Water–Energy–Milk Nexus: Empirical Evidence from Saudi Arabia" Water 16, no. 11: 1538. https://doi.org/10.3390/w16111538