We use the entropy balancing (EB) approach, developed by Hainmueller (2012) (see also Neuenkirch and Neumeier, 2016), to investigate empirically the effect of the GATT/WTO membership on income inequality and trade policy (the channel-variable). The EB approach is a non-parametric multivariate reweighting approach for impact analysis, which essentially aims to reweight the control group to match the moments of the treatment group in order to make the control group data match the covariate moments of the treatment. It is particularly useful here because member states that join the WTO are not randomly selected. As a result, it is hard to determine the extent to which the average treatment effects of the membership in the GATT/WTO on trade policy and income inequality are attributed to the membership itself or to the characteristics of each member state. The EB approach helps mitigate endogeneity concerns by severely reducing the bias introduced by the selection into the treatment. Its utilization involves two steps. In the first step, we compute the weights to assign to the control units based on the pre-treatment characteristics of units under analysis. In the present analysis, the balancing requirements are achieved by using the mean (average) of covariates to ensure that countries in the control group (non-WTO Members) are as similar as possible to countries in the treatment group (i.e., WTO Members). The weights are determined by using as observable pre-treatment characteristics of countries the macroeconomic determinants of accession to the GATT/WTO. Since we aim to ensure that the control group closely matches the treatment group, we follow for example Tang and Wei (2010) and Brotto et al. (2021), and do not include developed countries (at the time of accession) in our full sample. Thus, our full sample contains essentially developing countries, with the treatment group comprising GATT/WTO Members (taking into account the year of accession to the GATT/WTO), and the control group including WTO non-Members, that is, states that are either in the process of joining the WTO (i.e., WTO Observers) or those that have not even initiated the process of accession to the WTO.
Drawing from the relevant literature (e.g., Copelovitch and Ohls, 2012; Davis and Wilf, 2017; Jones and Gai, 2013; Wong and Yu, 2015; Tang and Wei, 2009), the observable pre-treatment characteristics of countries include the applicant’s market (economic) size and wealth (e.g., Copelovitch and Ohls, 2012; Davis and Wilf, 2017; Wong and Yu, 2015), its economic growth (e.g., Wong and Yu, 2015) and it’s the level of democracy (which also acts as a proxy for institution and governance quality) (e.g., Jones and Gai, 2013; Mansfield et al., 2002) and the terms of trade. Following Neuenkirch and Neumeier (2016), we use the one-year lag of these variables. We measure the economic size by the real Gross Domestic Product (GDP) (in natural logarithm), and the wealth by the real GDP per capita (in natural logarithm). These two variables and the economic growth indicator are sourced from the World Development Indicators (WDI) of the World Bank. The institutional and governance quality indicator was computed as the first principal component (based on factor analysis) of the six indicators of governance and institutional quality developed by the World Bank Governance Indicators developed by Kaufmann et al. (2010). Table 1 presents the results of the sample means of the matching covariates after weighing. We observe that the reweighed means of covariates (see column [4]) are identical to the target values of the same covariates (column [1]). Moreover, the standardized difference between the target value and the balanced value is essentially zero for all variables (column [5]).
Table 1
| Target Value | Unbalanced | Balanced |
| (1) | (2) | (3) | (4) | (5) |
| | Value | Standardized difference | Value | Standardized difference |
GROWTHt−1 | 3.883 | 4.781 | 0.094 | 3.883 | 0 |
Log(GDP)t−1 | 24.000 | 23.287 | -0.357 | 24.000 | 1.78e-15 |
Log(GDPC)t−1 | 7.809 | 7.536 | -0.281 | 7.809 | 9.16e-16 |
POLITYt−1 | 2.431 | -2.012 | -0.712 | 2.431 | -7.12e-17 |
TERMS | 117.117 | 119.563 | 0.057 | 117.117 | 0 |
[Insert Table 1, here]
In the second step, we use the computed weights to construct the entropy-balanced sample, which is in turn, utilized to run regressions where the treatment variable (the time - year - of membership in the GATT/WTO, defined as “Treat”) is the regressor, and the dependent variable is either the indicator of trade policy or income inequality. The coefficient of the treatment variable captures the average difference in the dependent (outcome) variable (trade policy, or income inequality) between GATT/WTO Members and NonWTO Members that is attributed to the membership in the GATT/WTO. Specifically, we estimate, on the one hand, the model specification that allows investigating the effect of the GATT/WTO membership on trade policy (see model (1)). On the other hand, we estimate the model specification that helps examine the effect of the GATT/WTO membership on income inequality (see model (2)).
Building on the literature on the macroeconomic determinants of trade policy (e.g., Milner and Kubota, 2005; Rose, 2013; Svaleryd and Vlachos, 2002), we postulate model (1) as follows:
$$\:{MATR}_{it}={\alpha\:}_{0}+{\alpha\:}_{1}{MATR}_{it-1}+{\alpha\:}_{2}{Treat}_{it}+\theta\:{X}_{it}+{\gamma\:}_{t}+{\mu\:}_{i}+{\epsilon\:}_{it}$$
1
Building on the voluminous literature on the determinants of income inequality (e.g., Amponsah et al., 2023; Brei et al., 2023; Furceri and Ostry, 2019; Jaumotte et al., 2013; Liu et al., 2023), we postulate model (2) as follows:
$$\:{GINI}_{it}={\beta\:}_{0}+{\beta\:}_{1}{GINI}_{it-1}+{\beta\:}_{2}{Treat}_{it}+\delta\:{Z}_{it}+{\gamma\:}_{t}+{\mu\:}_{i}+{\vartheta\:}_{it}$$
1
In equations (1) and (2), i represents a country and t stands for a year in the unbalanced panel dataset, which is constructed on the basis of data availability. It contains 117 countries in the treatment group, and 15 countries in the control group, over the annual period from 1980 to 2021. The dependent variables “MATR” and “GINI” are respectively the indicators of trade policy, and income inequality. Trade policy is measured by the “Measure of Aggregate Trade Restrictions” developed by the International Monetary Fund (IMF) (see Estefania-Flores et al. 2022). It provides granular measures of different facets of trade protectionism, including tariffs, non-tariff barriers, and restrictions on requiring, obtaining, and using foreign exchange for current transactions (see Estefania-Flores et al., 2023: p747). It has many advantages over existing trade policy indicators, one of these advantages being its far larger time coverage. This indicator has now been utilized in literature because it is simple, and relies on sensible, plausible, trade policy inputs obtained from a transparent and reliable source, which is easily accessible (for example, Campos et al., 2023). Lower values of this index indicate a greater trade policy liberalization (Data is available online at: https://sites.google.com/view/m-atr/). Income inequality is measured by the market Gini income inequality, i.e., income inequality before taxes and transfers. The values of this indicator range from 0 to 100, with higher values reflecting a more unequal income distribution. Data on the income inequality indicator were extracted from the Standardized World Income Inequality Database (SWIID) - SWIID - Version 8.0, February 2019 (see Solt, 2019 - available online at: https://fsolt.org/swiid/ ).
The one-year lag of the dependent variable is introduced in models (1) and (2) to take into account the inertia in these variables. \(\:{\alpha\:}_{0}\:\)to \(\:{\alpha\:}_{2};\:{\beta\:}_{0}\) to \(\:{\beta\:}_{2}\) as well as \(\:\theta\:\) and \(\:\delta\:\) are coefficients to be estimated. Specifically, \(\:{\alpha\:}_{2}\:\)represents the average treatment effect of the GATT/WTO membership on trade policy, and \(\:{\beta\:}_{2}\) is the average treatment effect of the GATT/WTO membership on income inequality. \(\:{\gamma\:}_{t}\) are temporal dummies, and \(\:{\mu\:}_{i}\) are countries' time invariant specific effects. \(\:{\epsilon\:}_{it}\) and \(\:{\vartheta\:}_{it}\:\)are two different well-behaving error terms.
\(\:\theta\:\) and \(\:\delta\:\) are respectively two different vectors of parameters \(\:\beta\:\) that include coefficients relating respectively to the vector of control variables \(\:{X}_{it}\) and \(\:{Z}_{it}\). Following Neuenkirch and Neumeier (2016), both \(\:{X}_{it}\) and \(\:{Z}_{it}\) include the variables used in the EB approach’s first step. \(\:{X}_{it}\) additionally includes the one-year lag of an indicator of financial development (see the literature on the macroeconomic determinants of trade policy), measured by the share of the domestic credit to private sector by banks in GDP. Data on this indicator were collected from the WDI.
\(\:{Z}_{it}\) includes in addition to the indicator of financial development, the squared term of the natural logarithm of the real GDP per capita. This is to capture the existence of a non-linear - inverted U-curve - relationship between the real per capita GDP and the level of income inequality (Kuznets, 1955).
We estimate models (1) and (2) and their different variants (see below) using the panel-corrected standard error (PCSE) estimator. This technique allows controlling for heteroscedasticity, first-order autocorrelation, and for contemporaneous correlation across individuals in the panel dataset (e.g., Beck and Katz, 1995, 1996).
We start by estimating models (1) and (2) over the full sample (see results in column [1] of Tables 2 and 3). We, then, examine the differentiated effects of the GATT/WTO membership on trade policy and income inequality in poorest countries (least developed countries – LDCs) versus NonLDCs in the sample (see results in column [2] of Tables 2 and 3). Next, we consider the differentiated effects of the GATT/WTO membership on trade policy and income inequality in African countries versus NonAfrican countries in the sample (see results in column [3] of Tables 2 and 3), given that African countries have the highest degrees of trade restrictiveness (see Estefania-Flores et al., 2022).
Table 2
Effect of the GATT/WTO Membership on Trade Policy Estimator: PCSE with panel specific first order autocorrelation (AR1)
Variables | (1) | (2) | (3) | (4) |
MATRt−1 | 0.0977*** | 0.0968*** | 0.0987*** | 0.0963*** |
| (0.0112) | (0.0113) | (0.0113) | (0.0109) |
Treat | -7.344*** | -11.60*** | -9.635*** | -4.568*** |
| (1.019) | (1.431) | (1.403) | (1.599) |
Treat*LDC | | 7.650*** | | |
| | (1.304) | | |
LDC | | -4.771*** | | |
| | (1.519) | | |
Treat*Africa | | | 4.843*** | |
| | | (1.174) | |
Africa | | | -1.178 | |
| | | (1.108) | |
Treat*ART26 | | | | -0.244 |
| | | | (1.407) |
ART26 | | | | 0.725 |
| | | | (1.337) |
Treat*NonART26 | | | | -10.19*** |
| | | | (1.585) |
NonART26 | | | | 6.395*** |
| | | | (1.488) |
Observations-Countries | 3,403 − 132 | 3,403 − 132 | 3,403 − 132 | 3,403 − 132 |
Pseudo-R2 / R2 | 0.971 | 0.973 | 0.971 | 0.972 |
Wald Chi2-Statistic (P-value) | 23337.96 (0.0000) | 27113.86 (0.0000) | 23660.19 (0.0000) | 28804.15 (0.0000) |
Note: *p-value < 0.1; **p-value < 0.05; ***p-value < 0.01. Robust standard errors are in parenthesis. Time dummies have been included in the regressions. The Pseudo R2 is reported for the outcomes arising from the FGLS-based regressions, and was calculated as the correlation coefficient between the dependent variable and its predicted values. The R2 is reported for regressions based on the PCSE estimator. |
Table 3
Effect of the GATT/WTO Membership on Income Inequality Estimator: PCSE with panel specific first order autocorrelation (AR1)
Variables | (1) | (2) | (3) | (4) |
GINIMt−1 | 0.0299*** | 0.0278*** | 0.0298*** | 0.0311*** |
| (0.00491) | (0.00476) | (0.00468) | (0.00474) |
Treat | -6.810*** | -13.35*** | -11.31*** | -9.033*** |
| (1.593) | (2.172) | (2.099) | (2.174) |
Treat*LDC | | 12.25*** | | |
| | (2.027) | | |
LDC | | -4.556** | | |
| | (1.895) | | |
Treat*Africa | | | 7.686*** | |
| | | (1.825) | |
Africa | | | 2.001 | |
| | | (1.797) | |
Treat*ART26 | | | | -1.033 |
| | | | (2.493) |
ART26 | | | | 10.45*** |
| | | | (2.446) |
Treat*NonART26 | | | | -0.714 |
| | | | (2.531) |
NonART26 | | | | 1.947 |
| | | | (2.408) |
Observations-Countries | 2,788 − 127 | 2,788 − 127 | 2,788 − 127 | 2,788 − 127 |
Pseudo-R2 / R2 | 0.993 | 0.993 | 0.993 | 0.994 |
Wald Chi2-Statistic (P-value) | 75093.96 (0.0000) | 79016.53 (0.0000) | 80160.50 (0.0000) | 71790.26 (0.0000) |
Note: *p-value < 0.1; **p-value < 0.05; ***p-value < 0.01. Robust standard errors are in parenthesis. Time dummies have been included in the regressions. The Pseudo R2 is reported for the outcomes arising from the FGLS-based regressions, and was calculated as the correlation coefficient between the dependent variable and its predicted values. The R2 is reported for regressions based on the PCSE estimator. |
Finally, we examine whether there are differentiated effects of GATT/WTO membership on trade policy and income inequality depending on member states’ commitments to trade policy liberalization. To address this question, we consider three groups of members states with different degrees of liberalization commitments. The first group includes countries that were essentially former colonies, and had neither undergone long negotiation processes, nor undertaken extensive policy reforms commitments when joining the GATT. This group is, henceforth, referred to as Article26 member states (“ART26”). The second group of countries comprises countries that did not invoke GATT Article XXVI 5(c) when joining the GATT. These countries (referred to as "NonArticle 26 member states") underwent long negotiation processes, and carried extensive reforms. The third and last group of countries are those that did not join the GATT, but joined the WTO, especially under Article XII of the Marrakesh Agreement establishing the WTO. This set of countries (referred to as Article12 countries - defined as “ART12”) underwent more stringent procedures than the ones undergone by original WTO Members (i.e., contracting parties of the GATT) (e.g., Drabek and Bacchetta, 2004). To address empirically our question, we create two dummy variables, one for Article26 member states, and another for NonArt26 members states, and introduce them in models (1) and (2) along with their interaction with the variable “Treat”. Therefore, the reference group in the regressions is Article 12 member states. Results of the estimation of this model specification are reported in column [4] of Tables 2 and 3.