3.1. Models’ Specification and Variables Definitions
The early literature dealing with banking stability relied on single soundness indicators, such as the capital adequacy ratio or the standard deviation of return on assets [
78]. However, various scholars pointed out the incapacity of a single financial indicator to reflect the variety of risks affecting banking activity and emphasized the importance of developing a composite stability index [
79]. In this respect, the Turkish Central Bank (2006) [
80,
81] developed a financial strength index encompassing six sub-indices reflecting, respectively, interest rate risk, foreign exchange risk, profitability, capital adequacy, asset quality and liquidity. Similarly Gersl and Hermanek [
82] developed an aggregate index based on six financial indicators. The weights associated with these partial indicators are based on experts’ judgments. The Overall financial strength index (OFSI), developed by Doumpos, Gaganis and Pasiouras [
78], is a weighted average of five financial criteria reflecting the CAMEL framework. The optimal weights associated with the five variables are determined via a Monte Carlo simulation. Accordingly, banks are classified into five categories from very weak to very strong.
The main advantage of this indicator is that it reflects various dimensions of the banking activity: profitability (via the average return on assets ratio), management quality (assessed through the cost ratio), capitalization (through the capital adequacy ratio), asset quality (gauged by the loans loss provision ratio) and liquidity risk (measured by the liquid assets ratio). It provides, therefore, a global evaluation of a bank’s soundness. However, this indicator suffers from important shortcomings. Firstly, the construction of this index requires a very large number of simulations and relies on ad hoc assumptions regarding the weights assigned to the variables and banks’ risk aversion. Secondly, the OFSI does not take into consideration the risks associated with foreign liabilities, including exchange risk, which became a source of growing instability for banks due to the rapid pace of international financial integration. Thirdly, the financial ratios should be normalized when introduced in the composite index to obtain equal variances for all of them. This is not the case with the OFSI, which considers the levels of the financial ratios. Finally, the OFSI considers simultaneously variables capturing the sources of risk and others reflecting the capacity of the bank to absorb these risks, which seriously affects the coherence of this index. For instance, an increase in the Capital Adequacy Ratio (CAR), Return on Assets (ROA), and Liquidity Ratio is associated with sounder banks, while an increase in the Cost to Income Ratio and the Problem Loans Ratio indicates a deterioration of the bank’s stability. An increase in the OFSI is, therefore, ambiguous to interpret.
To overcome these drawbacks, this study relies on two fragility indicators: the Banking Fragility Index (BFI) developed by Kibritçioğlu [
83] and the traditional Zscore. First, these indicators are complementary, since the FBI captures the sources of risk, while the Zscore reflects the capacity of the bank to absorb these risks. Together, they offer a complete picture of a bank’s soundness by assessing both its risk exposure and its capacity to face this risk. Secondly, comparing the estimation outcomes yielded by two different stability indicators should ensure the robustness of our results.
The main objective of this study is to investigate if an increased presence of female directors contributes to lowering the default probability of banking firms operating in the MENA region. We also aim to check if introducing internal governance mechanisms among the independent variables may enhance the predictive power of the model and lead to a more efficient EWS. To achieve these goals, we estimate the following model:
where
α0 is the constant term,
βi coefficients associated with the independent variables,
υi an individual random effect relative to bank
i and
εit the error term.
Crisisit is a dummy variable which takes 1 if bank
i is considered as highly exposed to insolvency risk in period
t and 0 otherwise. Various methodologies have been implemented to identify episodes of high banking instability. Following a strand of the previous studies [
83,
84], we opt for the Banking Fragility Index (
BFI) to identify periods during which banks are suffering from financial distress. This indicator is defined as follows:
where
CPSit,
FLit, and
DEPit represent the annual rates of change in Claims on Private Sector, Foreign Liabilities and Deposits, respectively, while
μ and
σ stand for their mean values and standard deviations. The underlying assumption of this indicator is that banking crises are characterized by high deposit withdrawals (banking runs), a sharp drop in claims in the private sector (due to an increase in non-performing loans), and a strong decrease in foreign liabilities (due to the depreciation of the domestic currency). The simultaneous occurrence of these three events clearly indicates that the bank is facing major financial difficulties. The main advantage of this indicator is that it covers a large scope of risks, as it assesses the bank’s exposure to the credit risk, the liquidity risk, and the currency risk simultaneously. A fall in the BFI can be interpreted as an increase in banking fragility. A negative BFI is a sign of financial fragility as it indicates that one or more variables composing the index are below their average values. Banks are supposed to be facing moderate fragility if the index ranges between 0 and −0.5, while they are considered as suffering from high fragility if the BFI’s value is less than −0.5.
In a second step, we try to assess the determinants of banking stability, while retaining the Zscore as a dependent variable:
The Zscore corresponds to the sum of the return on assets and the equity-to-assets ratios divided by the standard deviation of the return on assets. Following Delis, Hasan and Kazakis [
85] a five-year rolling time window is used to calculate the standard deviation of the ROA. Banks with lower values of the Zscore are considered highly exposed to insolvency risk, while higher Zscores are associated with more resilient banks. The advantages of using the Zscore as a dependent variable is threefold:
The variable Crisis is a dummy variable. It allows us to identify the independent variables producing a significant effect on banking stability to the point of tipping into a situation of financial distress. In contrast, the Zscore is a continuous variable, and thus makes it possible to better account for the impact of all the explanatory variables on banking stability, no matter how small.
Including the lagged Zscore among the independent variables is crucial because it is likely that banks that have recently experienced high instability are more prone to be subject to financial turmoil during the current period. That is, banking stability is highly persistent [
86].
Comparing estimation outcomes of models 1 and 2 should help identify the variables that have the greatest impact on banking stability and confirm the robustness of the results provided by Model (1).
The set of independent variables reflects the characteristics of the board of directors: the board’s size, the percentage of female directors, the percentage of independent directors, the number of board’s meetings, the number of committees, the attendance rate at the board’s meetings, and the number of the audit committee’s meetings. Larger boards and higher percentages of female and independent directors are expected to boost the exchange of ideas within the board, thereby leading to better decision-making and higher stability. More meetings and committees and a higher attendance rate are associated with tighter monitoring and should, therefore, contribute to enhancing stability.
The control variables include the bank’s financial variables, which capture instability stemming from bank-specific characteristics, and macroeconomic variables, which control for differences in cross-country economic risk. The bank’s size (Assets) produces an ambiguous effect on stability. Large banks benefit from economies of scale [
87], and enjoy lower financing costs and high market shares, which should boost their revenues and positively impact their stability. However, the too big to fail theory argues that big banks trigger a moral hazard problem, as they engage in risky strategies expecting that the cost of a banking failure would be mutualized over the whole banking system. Other studies highlighted that, above a critical size, banks should incur diseconomies of scale. The capital adequacy ratio (CAR) should spur stability, as better-capitalized banks are less exposed to insolvency risk. Similarly, holding more liquid assets (Liq) should enhance soundness by protecting banks against liquidity risk. However, liquid assets provide low returns, which may deteriorate performance and thereby stability. High cost-to-income ratios (CIR) reflect a deteriorated management efficiency and should therefore increase the default probability. Banks exhibiting high loan-to-assets ratios (Loans) should enjoy high-interest income, but are seriously exposed to credit risk. Finally, higher profitability, proxied by the return on assets ratio (ROE), should contribute to enhancing the bank’s soundness.
At the macro level, banks are expected to achieve better performance during high growth periods, which increases their resilience. At the same time, boom periods are characterized by the prevalence of adverse selection problems during the credit-granting process, which is detrimental to banking stability. On the other hand, a sharp deterioration of the macroeconomic environment should naturally lead to a stronger probability of default. The inflation rate is a widely used proxy for macroeconomic instability.
Table 2 summarizes the definitions of the variables included in models (1) and (2).
3.2. Sample and Methodology
The conventional econometric methods assume that the dependent variable is continuous and unbounded, which is not the case with Model (1). We therefore use logistic regression, well suited for binary outcomes such as bank default. The odds ratios are reported in
Table A2 to enhance interpretability. As a robustness check, we also estimated a probit model, an alternative specification for binary data. The probit results were highly consistent with the logit model, showing no meaningful differences in sign, magnitude, or statistical significance. These checks confirm the robustness and practical relevance of our findings.
An Early Warning System (EWS) intends to estimate the probability of the occurrence of a banking failure. The dependent variable is bounded (ranges between 0 and 1), while the outcome of the estimated equation is limitless (the predicted value may vary from −∞ to +∞). To overcome this problem, a transformation is applied to the predicted values of the dependent variable to transform them into probabilities. Let
Zit be the outcome of the estimated equation:
Zit may vary from −∞ to +∞. However, the following transformation of
Zit yields values ranging between 0 and 1:
This transformation stands for the probability that the dependent variable,
Yit, takes the value 1 conditional on the information contained in the set of independent variables,
Xit. Finally, a logistic transformation is applied to this probability to obtain the following model:
The model is estimated by applying the Maximum Likelihood method. Following the literature, we retain a fragility prediction threshold of 0.5 (Crisis
it takes 1 if P
it > 0.5). The performance of the Logit model is assessed through the prediction accuracy in
Table 3, which summarizes the overall error rates. Two types of errors can be associated with an early warning system: misidentification of fragility on one side and false alarms on the other side. The best specification is the one that minimizes both types of errors.
Results provided by the Logistic regression may be seriously affected by an endogeneity problem stemming mainly from reverse causality. To confirm the robustness of our results, we estimate Model (2) while applying the System GMM estimator which controls for endogeneity. Model (2) also offers the possibility to capture the persistence of turmoil periods by introducing a dynamic term in the model. Estimation methods designed for static models (i.e., fixed and random effects) are not suitable for Model (2), which includes the lagged dependent variable among the independent variables. In this case, applying the
within or the
FGLS estimators may lead to inconsistent results due to the autocorrelation between the dynamic term and the error term. Moreover, endogeneity stemming from reversed causality between the Zscore and some independent variables may lead to biased estimates. The difference-GMM estimator developed by Arellano and Bond [
88] deals with endogeneity and autocorrelation. This estimator removes the bank-specific effects and uses the lagged levels as instruments of the differenced variables. However, the second and higher order lags are often weak instruments of the difference variables, which reduces the robustness and the efficiency of the difference-GMM estimator. Alternatively, we use the System-GMM estimator developed by Arellano and Bover [
89] and Blundell and Bond [
90], which estimates a system composed of the difference and level equations and specifies a different set of instruments for each of them. The System-GMM estimator is more efficient, particularly when the dependent variable is highly persistent, which is likely to be the case in our model. The validity of the System-GMM estimators relies upon two tests: (i) the Arellano and Bond [
88] test confirming the null hypothesis of no second-order serial correlation in residuals; (ii) the Sargan/Hansen test used to confirm the overall validity of instruments (the null hypothesis states that instruments are jointly exogenous and are not correlated with the residuals).
Our final sample includes 61 commercial banks from nine MENA countries: Bahrain, United Arab Emirates, Kuwait, Oman, Qatar, Saudi Arabia, Tunisia, Morocco, and Egypt and covering 2012–2020 (
Table A1 and
Table 4). Data was compiled from banks’ annual reports, InvestingPro, Thomson Reuters, and the World Bank Development Indicators. The size of the sample reflects the limited availability of consistent data on women’s board representation, which we collected manually and retained only for banks reporting this information across the full period. We also excluded Islamic banks and commercial banks with Islamic windows to ensure model comparability, which reduced coverage in Gulf states. Islamic and conventional banks are characterized by different economic models and present, therefore, different risk profiles. For instance, Islamic banks are exposed to specific risks, such as the Shariaa compliance risk, which is not relevant for conventional banks. Moreover, all the Islamic financial instruments are backed by real assets. As a result, Islamic banks are less exposed to the credit risk and more sensitive to negative chocks affecting the real economy. We also note that Islamic banks do not have access to the hedging instruments that are banned by the Shariaa rules. The risks associated with these two categories of banks should, therefore, be modeled separately to take into consideration their specificities.
Countries such as Sudan and Iran were excluded because their systems are fully Islamic, while Iraq, Libya, Syria, Palestine, and Yemen were omitted due to political instability and severe data gaps. These selection criteria, while limiting the sample size, ensure data consistency and robustness in addressing endogeneity and cultural heterogeneity.
3.3. Descriptive Statistics and Preliminary Diagnostics
Descriptive statistics related to the variables included in both models are summarized in
Table 4. We notice that gender diversity is very limited in the boards of MENA banks, with women representing only 8.39% of the board members.
Figure 1 confirms that this average percentage is quite stable over the sample period. It also shows that banks in MENA countries have chosen a diversification strategy geared more towards independent directors than towards gender diversity. The percentage of women on boards is very limited compared to the percentage of independent directors, which barely exceeds 25% over the sample period.
Figure 2 reveals a more alarming fact: in most banks, no women are appointed to the board of directors. These findings show the extent to which MENA countries are lagging in terms of gender diversity, particularly in the banking industry.
Despite the fact that the MENA region still lags behind in terms of gender diversity, a decisive step towards diversification has been made during the last decade. Annual data summarized in
Table 5 shows that a large number of banks have at least one woman on their boards. A more in-depth analysis reveals that at least one woman is present on the board of directors in 65.2% of the total number of observations over the sample period (311 out of the 477 available observations). According to the critical mass theory, a minimum of two female directors is required to influence the decision-making process within the board. This is the case in 28.1% of the observations (134 out of the 477 observations).
Although it cannot attest to causality, the correlation analysis may provide interesting insights into the relationship between the dependent and independent variables. It also allows for to detect potential colinearity problems, which may affect the robustness of the estimation results. As shown in
Table 6, the highest negative and significant correlation coefficient is the one associated with the percentage of female directors and the crisis dummy variable (−0.42). This result suggests that gender diversity is the control variable that contributes most to reducing the likelihood of a banking crisis. Among the internal governance mechanisms, we notice that the percentage of independent directors, the number of the board’s meetings, and the attendance rate at those meetings all significantly contribute to reducing the probability of default. Enhancing internal governance seems, therefore, to play a key role in preventing a banking crisis. However, the correlation coefficients associated with the Zscore (column 2) lead to a very different conclusion: none of the governance proxies contributes significantly to promoting banking stability.
One possible explanation for these contradictory results is the non-linear effect produced by the governance proxies on banking stability. To investigate the non-linearity issue, we calculated the mean values of the Zscore and the crisis dummy variable for different intervals of gender diversity. Results in
Table 7 and
Table 8 show that crisis occurs most during periods when banks are exhibiting weak percentages of female directors (0.55% on average), and that the percentage of crises declines as the percentage of female directors increases. Such results suggest the existence of a linear decreasing relationship between gender diversity and the probability of default. Oppositely, results in
Table 8 suggest that the average Zscore declines and then increases as the percentage of women on the board increases.
Figure 3 confirms the non-linear relationship between the Zscore and the percentage of female directors. The Kernal regression curve shows that gender diversity spurs stability for weak values of the Zcore and becomes detrimental to stability when the Zscore takes high values. In other words, gender diversity is beneficial for banking stability during periods of financial turmoil (weak Zscore), while it deters stability during tranquil periods (high Zscore). The variance inflation factors (VIF) associated with the independent variables are reported at the end of
Table 6 (the VIF values reported in the table correspond to fixed effects models, with the log of the Zscore as a dependent variable, and in which all the independent variables and governance proxies have been included simultaneously). We notice that despite the high value of some correlation coefficients, the model does not suffer from multicollinearity.