A survey of existing literature and empirical research results dealing with the relationship between foreign trade and economic performance and its growth was the first step of the objectives and methodology of this paper. The object of the analysis is the wood processing industry. A characteristic feature of the WPI is the processing of raw wood and wood products manufacturing at various stages of finalization. Within the classification of business activities of the EU (NACE), WPI consists of three sections that can be characterized from the view of value-added creation as follows:
3.2. Indicators and Methods
The indicators and methods used to assess the effects of international trade on economic growth applied in the relevant empirical studies were used at a macroeconomic level. For measurement and evaluation at a mesoeconomic (industry) level, the indicators needed to be modified. The terms of trade indicators could not be used because of input data unavailability.
Indicators representing economic performance of the industry are value added, profit, and their ratios to sales (value added rate and return on sales). The ratio indicators are suitable for a comparison of results in different countries.
The value-added rate (VAR) is the value added to the total turnover of the sector and can be calculated as follows (
Sujová et al. 2015c):
where
VA is value added of the sector and
S—sales of the sector.
Return on sales (ROS) is a measure of how efficiently a company turns sales into profits. ROS is calculated by dividing operating profit by net sales (
Sujová et al. 2015c):
where
P is profit before tax of the sector and
S—sales of the sector.
The next analysis was focused on the foreign trade of the industry by quantifying (1) the export share of WPI to the whole industry, (2) the share of WPI import to its export, (3) the ratio of the sector export to its sales, and (4) the comparative advantages of the WPI. The comparative advantages were identified by a modified RCA indicator of a revealed comparative advantage (RCA). The RCA indicator represents the trade competitiveness and the following calculation formula is used (
Aiginger and Landesmann 2002):
where
xij is the export of industry “
i” in country “
j”;
mij is the import of industry “
i” in country “
j”;
Xj is total exports from country “
j”; and
Mj is the total imports to country “
j”.
If the value RCA < 0, it indicates a comparative disadvantage of the industry; if RCA > 0, the export of the industry and its commodities has a comparative advantage in the country, and RCA > 1 identifies that industry is competitive on international markets.
The growth rate of parts of a trade balance (
GX) expresses the development trend in foreign trade indicators. It was needed to calculate them for the analysis and correct interpretation of the obtained results:
where
X is the value of a part in the trade balance (export, import, and net export),
t is the period (year).
The positive value of G indicates the growth of import, export or net export, the negative values mean the decrease of indicators.
The relationship between economic indicators of WPI and components of foreign trade (import and export) of the industry were examined by multivariate linear regression (MLR) analysis. MLR method is used to assess the association between two or more independent variables and a single continuous dependent variable. The multiple linear regression equation in the analysis was as follows:
where Y is the economic indicator (sales, value added, or profit before tax) of industry as predicted or expected value of the dependent variable,
X1 (import volume) and
X2 (export volume) are distinct independent or predictor variables,
β0 is the value of Y when the independent variables (
X1 and
X2) are equal to zero, and
β1 and
β2 are the estimated regression coefficients.
Each regression coefficient represents the change in Y relative to a one-unit change in the respective independent variable. In the multiple regression situation, β1 is the change in Y relative to a one-unit change in X1, holding all other independent variables constant (i.e., when the remaining independent variables are held at the same value or are fixed). Statistical tests can be performed to assess whether each regression coefficient is significantly different from zero.
Additive stochastic term
ut was assumed. The least squares method (OLS) was used to estimate the MLR parameters. The OLS method provides unbiased and efficient estimates if the classical assumptions of the regression model are met (see
Gujarati 2003).
In addition to the standard t and F tests used in regression model, statistical tests that check if autocorrelation exists in a time series were applied. One of the main assumptions in linear regression is that there is no correlation between consecutive residuals, it is assumed that the residuals are independent. The first order autocorrelation by the Ljung-Box test was tested (
Ljung and Box 1978). The Ljung-Box test is also appropriate for small samples. If the
p-value of the test is greater than 0.05, the residuals for the time series model are independent, which is often an assumption made when creating a model. The test statistic is:
where n is the sample size, Σ is taken as the sum of 1 to h, where h is the number of lags being tested, pk is the sample autocorrelation at lag k.
The test statistic Q follows a chi-square distribution with h degrees of freedom; that is, Q~X2(h). We reject the null hypothesis and say that the residuals of the model are not independently distributed if Q > X21−α, h.
The linear specification of the regression model is verifying by the Ramsey RESET test. It tests whether non-linear combinations of the fitted values help explain the response variable. The intuition behind the test is that if non-linear combinations of the explanatory variables have any power in explaining the response variable, the model is misspecified in the sense that the data generating process might be better approximated by a polynomial, or another non-linear functional form (
Ramsey 1969).
The normality of residuals was tested by the Jarque-Bera test. It is a goodness-of-fit test of whether sample data have the skewness and kurtosis matching a normal distribution. If it is far from zero, it signals the data do not have a normal distribution. According to
Hall et al. (
1995), when using this test along with multiple regression analysis the right estimate is:
where n is the number of observations and k is the number of regressors when examining residuals to an equation.
Annual data are used in the analysis; therefore, the ARCH testing is not required. All test procedures by the Ljung-Box test, Ramsey RESET test, and the Jarque-Bera test are discussed in
Greene (
2003).
At the same time, since we estimate the parameters of models where the variables are time series, to avoid the problem of spurious regression, used variables should be generated by stationary processes. Dickey–Fuller test is used to determine whether a unit root is present in an autoregressive model. The extension of the Dickey–Fuller test called the augmented Dickey–Fuller test (ADF) was used to test the stationarity of time series. ADF test removes all the structural effects (autocorrelation) in the time series and then tests using the same procedure. If the calculated tau value is less than the critical value in the table of critical values, then we have a significant result, and the time series is stationary (
Dickey and Fuller 1979).
If the time series is a stationary process, the Granger causality test can be performed using the level values of two (or more) variables. If it is not the case, then differencing, de-trending, or other techniques must first be employed before using the Granger causality test. The Granger causality test assumes that the information relevant to the prediction of the variables is contained in the time series data of these variables. It is tested whether the lagged values of x affect y and vice versa. The Granger causality test is very sensitive to the number of lags used in the analysis. The null hypothesis expresses that the parameter for the lagged explanatory variables is equal to zero. If a given
p-value is < significance level (0.05), we can reject the null hypothesis and conclude that x Granger causes y (
Granger 1969).
Multivariate Granger causality analysis is usually performed by fitting a vector autoregressive model (VAR) to the time series and consequently by the Johansen cointegration analysis or estimating the ARDL models. The short time series analyzed in the paper allow to create VAR model only by one lag and a consequent cointegration model is not possible to create.
The Granger causality test can determine whether one time series is useful in forecasting another. It may be found that one or neither variable Granger-causes the other or that each of two variable Granger-causes the other. It means that Granger causality can be unidirectional or bidirectional. The statistical analysis of MLR can indicate association between economic performance and foreign trade (import and export) under condition that one of a trade balance side does not change. However, the export and import volumes are changing simultaneously and a deeper analysis considering the dynamics in import and export development is needed to analyze the impacts of a trade balance on the economic indicators.
The next part of this phase was the design of indicators to measure the effects of foreign trade on industry performance by modifying macroeconomic indicators used by
Breda et al. (
2007) and
Hajnovičová (
2008). The contribution of foreign trade (CFT) to the economic growth of the industry was applied. The indicator quantifies the impact of a trade balance to annual growth of the economic indicator in industry. Its calculation formula is as follows:
where EX is industry’s export; IM is industry’s; and Y is an industry’s economic indicator (sales, value added, profit).
The values of CFT indicator show that trade balance has a positive impact on the industry’s economic performance if CFT ˃ 0 and the CFT ˂ 0 indicates the negative effect of net export on the industry’s economic indicator.
The second measure used in the study was the transformation effect of an economy (TEE). TEE indicates the relationship between import of input material (
Mi) and export of the industry (
Xj). Its calculation is expressed in Equation (9). The TEE index, needed for the appropriate interpretation of the results, is calculated in Equation (10).
Based on a calculation of the designed indicators, the paper assessed the effects of foreign trade on the performance of sectors WPI in Czechia and Slovakia for a ten-year period (2009–2018). Comparing the growth rates of imports, exports, and net exports (Gx) with values of CFT indicators, the effects of trade balance on industry’s economic indicators can be identified and analyzed in more detail.