Dynamic Causality of Strategic Risk of Indonesia Coal-based
Enterprises (Var Model Application)
AYI AHADIAT1, RIBHAN RIBHAN1, FITRA DHARMA2, FAJRIN SATRIA DWI KESUMAH1
Department of Management,
University of Lampung,
Bandar Lampung City,
INDONESIA
Department of Accounting,
University of Lampung,
Bandar Lampung City,
INDONESIA
Abstract: - Currently, coal is an energy source used as fuel for power plants, which produces 37% of global
electricity, and by 2040 it is predicted to produce 22% of the world's electricity. Therefore, the development of
a coal company's stock price can reflect companies’ management performances in controlling risk which in turn
can affect the level of volatility of the company's stock price and become an indicator for investors in making
investment decisions in order to get a return. tall one. The formulation of strategic risk of coal subsector
companies with the application of the vector autoregressive (VAR) model becomes the basis of this research,
where strategic risk is proxied through the growth of stock prices and returns in each coal company that is the
sample of the study. The method that will be used in this research is descriptive quantitative through the
application of the VAR model to be able to describe the causality relationship between companies. The results
obtained are the VAR(2) model of each coal subsector company, which is used as an initial identification of its
strategic risk so that the coal subsector company can make mitigation steps in dealing with these strategic risks.
Key-Words: VAR Model, Stock Return, Strategic Risk.
Received: March 25, 2023. Revised: July 4, 2023. Accepted: July 14, 2023. Published: July 27, 2023.
1 Introduction
Over time, the need for energy, especially coal will
increase so that many countries that do not have
sufficient natural energy resources to meet their
energy needs will import to meet their needs and
domestic stability, [1]. In addition, Indonesian coal
production is expected to continue to increase,
especially to meet domestic needs (power
generation and industry) and foreign demand
(exports), [2]. The development of coal production
for the period 2009-2018 experienced a considerable
increase, with production achievements in 2018 of
557 million tons. Of the total production, the export
portion of coal reached 357 million tons (63%) and
most of them was used to meet the demands of
China and India, [3]. Thereby, the high number of
Indonesian coal exports makes Indonesia one of the
largest coal exporters in the world besides Australia,
[4].
On the one hand, domestic coal consumption
reached 115 million tons or less than the domestic
coal consumption target of 121 million tons, [1].
One of the factors causing the lower realization of
coal consumption is the operation of several 35,000
MW Steam Power Plants (PLTU) programs that are
not in accordance with the plan and there are several
industrial activities that have decreased, [5].
On the other hand, coal companies have a fairly
high risk because from the exploration stage to
construction they have high uncertainty and very
large funds, [6]. Limited company resources and
limited access to banks to obtain additional funds
are problems faced by many companies, [7]. The
capital market provides a solution that can be
considered in terms of funding by changing the
company's status from a closed company to a public
company through an offering of shares to the public
(going public). Thus, the company will get funds
(capital) to run and develop its business, [8].
Therefore, the development of coal companies’
stock prices can reflect the company's management
performance in controlling risk which in turn can
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Ayi Ahadiat, Ribhan Ribhan,
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affect the level of volatility of the company's stock
prices and become an indicator for investors in
making investment decisions in order to get a high
return, [9]. The objective of this study then is to
examine the causal relationship of strategic risk of
stock returns of coal subsector companies in
Indonesia. The novelty of this study is in examining
the dynamic relationship of strategic risk caused by
the unstable rate of return between coal companies
in Indonesia.
2 Literature Review and Hypothesis
Development
Corporate risk management has been widely
studied, such as research conducted by, [10], which
revealed that BASEL III requires banks to mitigate
their strategic risks. In this study, two scenarios are
offered in terms of strategic risk management
control that can be applied in the banking world,
which are a comprehensive definition of strategic
risk itself, and a framework that uses the cost of
equity component to estimate the amount of
economic capital needed to mitigate the risk.
strategic risk. On the one hand, the framework
simulates the bank's net income and uses a Value at
Risk (VaR) approach to measure economic capital
requirements. The framework can also be used to
evaluate the impact of strategic changes in the
required economic capital, [11].
On the other hand, [12], in their empirical
research found that Vector Autoregressive (VAR)
(1) modelling is the best model to be applied in the
analysis of the dynamic relationship between Sharia
stock prices, sharia stock indexes, and changes in
the rupiah exchange rate against foreign currencies.
The results of their research also revealed that each
variable is only influenced by its respective
historical data, and the results of the impulse
response function indicated that the response of all
variables is difficult to reach the zero point or
equilibrium point after a shock to other variables
occurs in the short term. The VAR(1) modelling is
then used as a model to predict the data for each
variable for the next six months which shows the
results of the Sharia stock variable data and
currency exchange rates moving stable, and the
Islamic stock index is predicted to increase
significantly.
However, as far as observations, research on
strategic risk analyzed using the VAR approach in
coal-based companies has not been widely carried
out. For this reason, the state-of-the-art research that
we are going to do is to provide a causal relationship
model of stock returns in the coal subsector in
Indonesia in mitigating its strategic risk.
3 Research Methods
The variables analyzed in this study are the daily
stock return values of the selected sample of coal
subsector companies for the last 5 years from 2017
to 2021. The research sample was taken by
purposive sampling method, which was coal
subsector companies that have been listed on the
Indonesian stock exchange (IDX) during the
research period, and from the coal subsector
companies listed on the IDX. Samples were from 5
(five) coal subsector companies that have the largest
captive market shares. Then stock returns from each
research sample were used as input in the analysis
of causality between each variable by applying the
Vector Autoregressive (VAR) application.
VAR modelling can be done in several stages, as
follows:
a) Testing Stationary Data
In analysing time series data, the first thing to
check is whether the data is stationary or not. There
are two ways of testing stationary data, first visually
by looking at the graph of the time series data, and
second statistically by testing the Augmented
Dickey-Fuller Test (ADF Test) method, [13], with
the following equation.


and the hypothesis:
H0: = 0 (not stationary)
H1: > 0 (stationary)
The null hypothesis is rejected if it is less than -
2.57 or the probability value is less than 5%, [14].
b) Estimation of VAR Modelling
The process of VAR modelling on order p
(VAR(p)), can be written mathematically as follows,
[15]: 

Where k is 1,2, 3…, p; is the k x k matrix; and
can be described as follows, [16].
󰇭
󰇮
󰇯








󰇰󰇭

󰇮
c) Granger Causality Test (GCT)
The following is a bivariate of two variables as
an example (Ax and Bx), [17].
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 
 

 
 
[18], [19], described a linear model of Granger
causality, where if Granger Ax causes Bx, then
historical data Ax can predict Bx better than
historical data Bx alone.
d) Impulse Response Function (IRF)
Research conducted by [20], [21], measuring
unexpected events (shocks) or the effect of non-zero
residuals can be studied to see the relationship
between variables. This is because the VAR model
can translate shocks into variables using a non-zero
residual value if only if some structural restrictions
have been considered previously. [22], stated that
IRF is a function of understanding more deeply the
impact of changes in each variable in analysing
multivariate time series.
e) Forecasting Stock Return Value Data
The last stage in the VAR(p) model method is to
predict stock return value data from each variable
over a certain period, where the stock return value
of a company is influenced not only by the historical
data of the company itself but also can be influenced
by the historical data of other companies, taking into
account unexpected events during the period of the
study, [16].
4 Results and Discussion
The analysis in this study begins with a description.
Based on the formulation of the problem in this
study, the research sample was determined, namely
the state-owned coal subsector company, PT Bukit
Asam, Tbk and from a private company, PT Adaro
Energy, Tbk. The stock price data of the two
companies were obtained from the
www.yahoo.finance.com from 2017 to 2021 and
from the published annual reports of each company.
From the data collection, the return values of each
company were calculated which were used as the
basis for calculating and analyzing the causal
relationship on the strategic risk of stock returns in
coal subsector companies in Indonesia.
4.1 Stationary Conditions
Before estimating VAR modelling for PTBA and
ADRO stock returns, each observed data series
needs to be tested for stationary first. To run this
test, we checked visual and statistical tests to get
more valid results. Figure 1 shows a graph plotting
the data series of each variable. The graph visually
explains that the two data series are stationary
because the mean and variance are around zero,
respectively.
Furthermore, based on the baseline statistical
test, we apply the ADF unit-root test whereas, as
shown in Figure 2, both data series have a
probability value of less than 5% indicating they
have a unit-root which is measured as a stationary
data set.
Fig. 1: Distribution of PTBA and ADRO Stock Returns
Source: Processed data (EViews 10)
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Fig. 2: ADF unit-root test of PTBA and ADRO Stock Returns
Source: Processed data (EViews 10)
4.2 Optimal Lag Test
Determining the optimum lag in the VAR model is a
necessary initial test because it can explain the
dynamics model more accurately for the VAR
model. Figure 3 shows the results of the optimal lag
test for the estimation of the VAR model.
Furthermore, from the VAR Lag Order output, the
optimal lag length is then indicated by criteria
marked with an asterisk, and in this case, the
optimal lag length occurs in lag 2 (shown in Figure
3) because it has the highest number of criteria with
asterisks. Then, after getting the optimal lag length
in lag 2, the next step is to estimate the VAR lag 2
model, which is as Figure 4.
Fig. 3: Optimal Lag Testing of Var Model
Estimation
Source: Processed data (EViews 10)
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Fig. 4: Results of VAR Lag 2 Model Estimation
Source: Processed data (EViews 10)
4.3 Cointegration Test
After getting the optimal lag on the VAR model, the
next step is to perform a cointegration test on the
VAR model estimation. The criteria for the VAR
model to pass the cointegration test can be seen in
the Prob** value, if it is less than 0.05 then the
VAR model passes the cointegration test. The
following are the results of the cointegration test for
the estimation of the VAR model which has a
probability value of less than 0.05, as shown in
Figure 5.
Fig. 5: Johansen Cointegration Test Output
Source: Processed data (EViews 10)
4.4 VAR Model Estimation
The optimal lag value is 2, it can be said that the
VAR model estimation is the VAR(2) model. The
following is the estimation result of the VAR(2)
model for PTBA and ADRO stock returns, as shown
in Table 1, and Table 2.
Table 1. Output Estimated Model VAR(2) for the
dependent variable PTBA
Dependent Variable: PTBA
Method: Least Squares
Date: 09/13/22 Time: 15:06
Sample (adjusted): 1/07/2010 6/03/2021
Included observations: 2972 after adjustments
Coefficient
Std. Error
t-Statistic
Prob.
0.000273
0.000524
0.520554
0.6027
-0.019091
0.022478
-0.849290
0.3958
-0.033646
0.022477
-1.496879
0.1345
0.050669
0.024377
2.078513
0.0377
0.007461
0.024367
0.306168
0.7595
0.002310
Mean dependent var
0.000267
0.000965
S.D. dependent var
0.028579
0.028566
Akaike info criterion
-4.271539
2.421071
Schwarz criterion
-4.261449
6352.506
Hannan-Quinn criter.
-4.267908
1.717252
Durbin-Watson stat
1.996560
0.143286
Table 2. Output Estimated Model VAR(2) for the
dependent variable ADRO
Dependent Variable: ADRO
Method: Least Squares
Date: 09/13/22 Time: 15:10
Sample (adjusted): 1/07/2010 6/03/2021
Included observations: 2972 after adjustments
Coefficient
Std. Error
t-Statistic
Prob.
0.000103
0.000482
0.213163
0.8312
0.053627
0.020697
2.591063
0.0096
0.059703
0.020696
2.884790
0.0039
-0.027420
0.022445
-1.221614
0.2220
-0.063108
0.022436
-2.812768
0.0049
0.005452
Mean dependent var
0.000120
0.004111
S.D. dependent var
0.026356
0.026302
Akaike info criterion
-
4.436678
2.052525
Schwarz criterion
-
4.426589
6597.903
Hannan-Quinn criter.
-
4.433047
4.066038
Durbin-Watson stat
2.001770
0.002731
In the estimation output of the VAR(2) model for
the dependent variables PTBA and ADRO, it can be
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seen that not all order lags have a significant
coefficient, so the VAR(2) model for the dependent
variable PTBA becomes:
PTBA = 0.000273 + 0.050669*ADRO(-1)
For the VAR(2) model, the dependent variable
ADRO is:
ADRO = 0.000103 + 0.053627*PTBA(-1) +
0.059703*PTBA(-2) 0.063108*ADRO(-2)
From the VAR model equation above, it can be
concluded that PTBA stock returns are significantly
affected only by stock returns ADRO first lag.
Meanwhile, for the ADRO variable, the VAR(2)
model shows that ADRO stock returns are
significantly affected by PTBA stock returns in the
first and second lag and ADRO stock returns in the
second lag.
4.4 Granger Causality
The hypothesis of the Granger causality test is to
test whether the correlation value of a variable is
only influenced by itself and not by the historical
value of other variables. The following are the
results of the Granger causality test from the
VAR(2) model, as shown in Table 3.
Table 3. Granger Causality Test Statistics Model
VAR(2)
Pairwise Granger Causality Tests
Date: 09/13/22 Time: 15:26
Sample: 1/05/2010 6/03/2021
Lags: 2
Null Hypothesis:
Obs
F-Statistic
Prob.
ADRO does not Granger Cause PTBA
2972
2.18100
0.1131
PTBA does not Granger Cause ADRO
7.16395
0.0008
From the output of Granger Causality Tests
Model VAR(2) above, it can be concluded that the
PTBA variable with a probability value of more
than 0.05 PTBA return value variable is not
influenced by itself and is influenced by historical
data of other variables. Meanwhile, for the ADRO
stock return value variable with a probability value
less than 0.05, it can be said that ADRO's stock
return is influenced by its own historical data as
well as the historical data of other variables.
4.5 Forecasting Stock Return Value
The next step is to forecast the stock return value
from the estimated VAR(2) model. The following
graphs presented at Figure 6 illustrate the projected
stock return value of each variable.
-.0024
-.0020
-.0016
-.0012
-.0008
-.0004
.0000
.0004
.0008
4 7 8 9 10 11 14 15 16 17 18 21 22 23 24 25 28 29 30 1 2
M6 M7
PTBA_F
-.001
.000
.001
.002
.003
.004
.005
4 7 8 9 10 11 14 15 16 17 18 21 22 23 24 25 28 29 30 1 2
M6 M7
ADRO_F
Fig. 6: Forecasting of PTBA and ADRO Stock
Returns for the Next One Month
5 Conclusion
This study aims to examine more deeply the
implementation of strategic risk control which is
described by the stock returns of the coal production
subsector for each group of companies. This is
achieved by looking at the dynamic relationship
with the VAR model approach. We emphasize on
how the rate of return from one company is
influenced by the rate of return from each company,
thus, it can be used as a reference in future planning
of strategic risk. From the results of this study, the
most suitable model used to describe the
relationship is the VAR(2) model. Analytically, the
VAR(2) model can be applied to predict the
behaviour of each variable over the next 30 days.
On the one hand, it is worth mentioning that before
doing our forecasting analysis, the model was tested
for the univariate model using the Granger causality.
Based on the univariate model, our model shows
significant enhancements with a probability value of
less than zero. On the other hand, Granger causality
explains that each variable does not only affect itself
but is also influenced by other variables. Finally, the
forecasting model is very well fitted where the
prediction line closely matches the actual data plot,
which indicates that the VAR(2) model is the most
suitable model used for forecasting.
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Contribution of Individual Authors to the
Creation of a Scientific Article (Ghostwriting
Policy)
Ayi Ahadiat was the main conceptor of the study
and conducting analysis on discussion part.
Ribhan was responsible for writing introduction and
literature reviews.
Fitra Dharma and Fajrin Satria Dwi Kesumah
carried out collecting and analysis data.
Sources of Funding for Research Presented in a
Scientific Article or Scientific Article Itself
No funding was received for conducting this study.
Conflict of Interest
The authors have no conflict of interest to declare.
Creative Commons Attribution License 4.0
(Attribution 4.0 International, CC BY 4.0)
This article is published under the terms of the
Creative Commons Attribution License 4.0
https://creativecommons.org/licenses/by/4.0/deed.en
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