3.1- Model and econometric estimation approach
Based on recent research for a range of developing countries, our model is inspired by Candelise et al. (2021). The model is therefore as follows:
$${y}_{i,t}= {\alpha }_{i,t}+{x}_{i,t}\beta + { + \mu }_{i,t} + {v}_{i,t}+ {\epsilon }_{i,t } \left(1\right)$$
Where\({y}_{i,t}\), represents the dependent variables, \({\alpha }_{i}\) denotes country fixed effects, \({x}_{i,t}\)denotes independent variables, \(\beta\)denotes the coefficient estimate \({\epsilon }_{i,t }\) is the error term, i is the cross-sectional units and t is the period. As our sample consists of several countries, there is a presumption of heterogeneity in our panel. Therefore, it is necessary to take into account individual (country) heterogeneity. Due to this, we use the fixed effect model, which takes heterogeneity into account. By using fixed effects, we assume that each country has its own fixed effect. Errors are always homoscedastic, so specific effects are only taken into account at the residual level. Here is the empirical model:
$${FSI}_{i,t}= {\beta }_{0}+ {\beta }_{1}{EP}_{i,t}+ {\beta }_{2}{X}_{i,t}+ {\epsilon }_{i,t} \left(2\right)$$
The Food Security Index (FSI) measures food security, while energy poverty is measured by the Energy Development Index (EDI), access to electricity (Elec) and access to clean energy for cooking (Clean). \({X}_{i,t}\) it is the set of control variables and \({\epsilon }_{i,t}\) is the error term.
Fixed-effect models allow for heterogeneity as a result of the country effect. A cross-sectional dependency is also present in the panel data. For this reason, we use the Driscoll and Kraay estimation method. It may not be true that our variables have a static relationship as assumed by the fixed effect model or Driscoll and Kraay. Even though Driscoll and Kraay's fixed effects method is easy to implement, it does not account for unobserved heterogeneity. To address the question of endogeneity, we must either use the Lewbel 2SLS estimation method or rewrite our model dynamically. With Lewbel's technique, our results are more robust than when we use instrumental variables. Instrumental variable estimators are generally difficult to use in most applications due to the difficulty of finding suitable instruments that simultaneously satisfy these conditions (Baum et al., 2012; Stock et al., 2002). As a solution to this problem, we use Lewbel's two-stage least squares (2SLS) which is applied when sources of identification, like appropriate internal and external instruments, are unavailable. In the absence of traditional identification information, Lewbel's 2SLS approach is essential for identifying structural parameters in regression models with an endogenous or poorly measured regressor. Instruments based on heteroskedasticity are constructed in-house for this method. Lewbel's 2SLS approach has the advantage of not requiring standard exclusion restrictions to be met.
Accordingly, we apply a generalized method of moments (GMM), which was proposed by Arellano et Bond (1991), Arellano et Bover (1995), and Blundell et Bond (1998) so that the model's dynamics can also be verified. In a system, the Generalized Method of Moments (GMM-S) is used for several reasons. Heteroskedasticity, endogeneity, overidentification, and validity are all econometric problems that are frequently solved with the GMM-S method. The GMM-S method is more efficient at dealing with heteroskedasticity in empirical studies, according to Baum et al. (2012). The related literature uses GMM to assess instrument strength, according to Bazzi et Clemens (2013). The dynamic panel GMM, according to Roodman (2009), can lead to too many instrument problems. The rule of thumb is that the number of instruments should be smaller than the number of countries in order to solve this problem. In addition, the GMM has the advantage of treating all explanatory variables as instrumental variables according to their lagged values (in terms of level and first difference). Hence the following model:
$${FSI}_{i,t}= {\beta }_{0} +{FSI}_{i,t-1} + {\beta }_{1} {EP}_{i,t}+{\beta }_{2} {GDP/h}_{i,t}+ {\beta }_{3}{ Fixe/T}_{i,t}+ {\beta }_{4}+{\beta }_{5}+{ \beta }_{6} {CTC}_{i,t}+ {\beta }_{7}{DCPS}_{i,t}+ {\mu }_{i,t} + {v}_{i,t} + {\epsilon }_{i,t} \left(4\right)$$
In this paper, energy poverty and food security are examined using a two-step system of GMM.
3.2- Data source
From 2000 to 2020, we use 36 sub-Saharan African countries. In the empirical estimations, energy access, food security, and other control variables were used. The empirical estimations are based on the availability of our variables of interest and dependent variables, as well as other control variables. Appendix provides definitions and sources of our key variables. Principal Component Analysis (PCA) is used to construct the food security index. To better understand the food situation in Sub-Saharan Africa, sixteen variables were used to construct this index, taking into account the four dimensions of food security. FAOSTAT provides all of these variables. The variables used to measure energy poverty are access to electricity, access to clean energy for cooking, and an energy development index that was constructed based on the World Development Indicator. In terms of our control variables, they are presented in detail in the appendix, which also takes in the World Development Indicators.
On the food security index, the energy development index, access to electricity, and access to clean energy are positively correlated.
3.2.1. Dependent variable
To measure the dependent variable, a composite index is constructed using principal component analysis (PCA) (Slimane et al., 2016). There are four dimensions to consider: availability, accessibility, use and stability. By transforming correlated variables into uncorrelated variables, the PCA1 method aims to reduce the number of indicators.
3.2.2. Variables of interest
Energy poverty is defined by Acharya and Sadath, (2019); Thomson et al. (2016) as a lack of access to and use of modern energy services. Thus, this concept has been understood differently in the literature. Recently, Churchill and Smyth, (2021) refer to energy poverty as the impact of a lack of adequate access to energy on the objective or subjective well-being of a household. The subjective well-being of a household is reduced by energy deprivation and poor cooking and heating conditions. This may capture the utility of energy access for a household, but is often plagued by self-reporting bias and survey inconsistencies (Herrero, 2017).
In the opposite direction, energy poverty can be measured objectively by the proportion of households that spend a higher percentage of their income on energy bills, which makes them more economically vulnerable. This is particularly the specific case in developing countries (Boardman, 1991; Healy and Clinch, 2004; Hills, 2012; Tod and Thomson, 2017) such as sub-Saharan Africa. Nevertheless, these measures may suffer from sample selection bias, leading to over- or underestimation of energy poverty rates (Herrero, 2017). The IEA (2010) and Banerjee et al. (2021) constructed an energy development index (EDI) using geometric and arithmetic means, while we use principal component analysis. This index is based on three indicators covering the renewable energy sector. These three indicators are: 1) access to electricity; 2) consumption of renewable energy; and 3) access to clean energy for cooking.
3.2.3. Control variables
Gross domestic product per capita (GPD/h) can positively influence food security at the level of a country or a larger region such as SSA (Campi et al., 2021; Candelise et al., 2021). Information and communication technologies have positive effects on food security, particularly through the use of fixed-line telephones (Fixed-T) as demonstrated by Anser et al. (2021). Employment (EmplT) also influences the degree of household food security (McCordic et al., 2021). Population density (PopD) affects the ability of a region to better feed its population (Badami et Ramankutty, 2015; Vijay et Armsworth, 2021; Candelise et al., 2021). Governance as measured by Control of Corruption (CTC) influences policy measures taken to curb famine (Anser et al., 2021). Financial development (DCPS), measured by the volume of financial resources provided to the private sector by financial institutions. It increases the availability of credit and enables agricultural entrepreneurs to access financial resources that can enable them to invest more in the agricultural sector (Chisasa et Makina, 2012). Urban population growth (Urbpop) as noted by Candelise et al. (2021) is able to affect the level of food security. Finally, political stability (Spop) contributes to increasing the level of stability and availability of food (Ribeiro et al., 2021). Imports (Imp) also positively regulate the supply of food in a country (Candelise et al, 2021).
Variable
|
Abrev.
|
Obs
|
Mean
|
Std. Dev.
|
Min
|
Max
|
Data
|
Table 1
Food security Index
|
FSI
|
756
|
-3.97E-05
|
0.5414625
|
-1.47
|
1.64
|
FAOSTAT(2022)
|
Energy Development Index
|
EDI
|
756
|
0.0000397
|
0.0292986
|
-0.04
|
0.09
|
WDI(2022)
|
Access to electricity
|
ELEC
|
698
|
39.10533
|
24.86226
|
1.27018
|
100
|
WDI(2022)
|
Access to clean energy for cooking
|
clean
|
612
|
20.34379
|
24.47314
|
0.15
|
93.34
|
WDI(2022)
|
GDP per capita
|
GDP/h
|
739
|
1.739847
|
4.568149
|
-36.55692
|
28.676
|
WDI(2022)
|
Fixed-telephone
|
Fixed-T
|
726
|
4.258437
|
9.935925
|
0
|
59.98999
|
WDI(2022)
|
Employers total
|
EmplT
|
720
|
1.991056
|
1.57211
|
0.04
|
8.39
|
WDI(2022)
|
Population density
|
PopD
|
756
|
86.79749
|
118.8185
|
2.17977
|
623.5172
|
WDI(2022)
|
Control of corruption
|
CTC
|
720
|
34.42657
|
21.96376
|
0.5050505
|
84.84849
|
WGI(2022)
|
Domestic credit to private sector
|
DCPS
|
723
|
20.11717
|
18.24886
|
0.449183
|
106.2603
|
WDI(2022)
|
Imports of goods
|
Imp
|
676
|
42.47359
|
26.23712
|
4.829832
|
236.391
|
WDI(2022)
|
Urban population
|
Urb
|
756
|
42.6223
|
17.11767
|
14.61
|
90.092
|
WDI(2022)
|
Political stability
|
PST
|
720
|
35.28784
|
22.99568
|
0
|
93.75
|
WGI(2022)
|
Source : Authors |
The descriptive statistics show little variation, suggesting unbiased results.
Variables
|
(1)
|
(2)
|
(3)
|
(4)
|
(5)
|
(6)
|
(7)
|
(8)
|
(9)
|
(10)
|
Table 2
(1)FSI
|
1.000
|
|
|
|
|
|
|
|
|
|
(2)EDI
|
0.588
|
1.000
|
|
|
|
|
|
|
|
|
(3)ELEC
|
0.403
|
0.892
|
1.000
|
|
|
|
|
|
|
|
(4)Clean
|
0.260
|
0.937
|
0.793
|
1.000
|
|
|
|
|
|
|
(5)GDP/h
|
0.011
|
0.010
|
-0.023
|
0.010
|
1.000
|
|
|
|
|
|
(6)Fixe-T
|
0.213
|
0.218
|
0.061
|
0.224
|
-0.016
|
1.000
|
|
|
|
|
(7)EmplT
|
0.392
|
0.527
|
0.419
|
0.509
|
0.042
|
0.210
|
1.000
|
|
|
|
(8)PopD
|
0.320
|
0.291
|
0.334
|
0.231
|
0.116
|
-0.112
|
-0.066
|
1.000
|
|
|
(9)CTC
|
0.503
|
0.541
|
0.362
|
0.482
|
0.089
|
0.078
|
0.292
|
0.340
|
1.000
|
|
(10)DCPS
|
0.683
|
0.777
|
0.670
|
0.710
|
0.034
|
0.090
|
0.502
|
0.462
|
0.583
|
1.000
|
Source : Authors |
[1] All the variables used here are set out in the Annex