Table 1
Variables, definitions, data sources, and summary statistics
| Variables | Definition | Data Source | Num. of Observation | Mean | Std. Dev. |
|---|---|---|---|---|---|
| ECI | Economic complexity index | Harvard MIT (2022) | 76 | 1.2642 | 0.2606 |
| GL_HT | GL-index with Germany for high-tech product clusters | Authors' calculations based on Trade Map (2021) | 76 | 0.3097 | 0.0953 |
| GL_MT | GL-index with Germany for mid-tech product clusters | as above | 76 | 0.4728 | 0.0959 |
| GL_LT | GL-index with Germany for low-tech product clusters | as above | 76 | 0.4364 | 0.0609 |
| VERTHQ_HT | Vertical trade/high quality with Germany for high-tech product clusters | as above | 76 | 0.1180 | 0.0544 |
| VERTHQ_MT | Vertical trade/high quality with Germany for mid-tech product clusters | as above | 76 | 0.1655 | 0.0458 |
| VERTHQ_LT | Vertical trade/high quality with Germany for low-tech product clusters | as above | 76 | 0.1131 | 0.0302 |
| Fdi | Foreign direct investment, net inflows (% of GDP) | World Bank | 76 | 5.9880 | 12.9742 |
| LogImport | Logarithm of share of intermediate and capital goods imports in total imports from Germany | Authors' calculations based on UN Comtrade (2022) | 76 | 1.9255 | 0.0195 |
| LogRD | Logarithm of gross domestic spending on R&D (% of GDP) | OECD | 76 | −0.0234 | 0.1756 |
| LogResearcher | Logarithm of researchers per 1000 employed | as above | 76 | 0.7239 | 0.1103 |
[i] Source: Authors' own calculations

Figure 1
The GL-index of V4 countries in trade with Germany in low-tech goods (2001–2019).
Source: Authors' own calculations based on Trade Map (2021).

Figure 2
The GL index of V4 countries in trade with Germany in mid-tech goods (2001–2019).
Source: Authors' own calculations based on Trade Map (2021).

Figure 3
The GL index of V4 countries in trade with Germany in high-tech goods (2001–2019)
Source: Authors' own calculations based on Trade Map (2021).

Figure 4
The GL-index of V4 countries in high-quality vertical trade with Germany in low-tech goods (2001–2019).
Source: Authors' own calculations based on Trade Map (2021).

Figure 5
The GL-index of V4 countries in high-quality vertical trade with Germany in mid-tech goods (2001–2019).
Source: Authors' own calculations based on Trade Map (2021).

Figure 6
The GL index of V4 countries in high-quality vertical trade with Germany in high-tech goods (2001–2019).
Source: Authors' own calculations based on Trade Map (2021).
Table 2
Unit root test results
| CADF Unit Root Test | ||
|---|---|---|
| Variables | CIPS Statistics | |
| Level | 1st difference | |
| ECI | −3.717*** | - |
| GL_HT | −2.758* | - |
| GL_MT | −1.21 | −3.724*** |
| GL_LT | −1.30 | −4.126*** |
| LogImport | −2.886** | - |
| LogRD | −2.34 | −4.113*** |
| LogResearcher | −2.93** | - |
| VERTHQ_HT | −3.062** | - |
| Im-Pesaran-Shin Unit Root Test | ||
| Variables | Intercept | Intercept - Trend |
| Fdi | −4.23201*** | −4.08435*** |
| VERTHQ_MT | −2.00021** | −2.20049** |
| VERTHQ_LT | −1.36331 | −0.64119 |
| Δ VERTHQ_LT | −8.86728*** | −7.62207*** |
[i] ***, ** and * refer to 1%, 5% and 10% significant levels, respectively. The critical values for CADF test are −3.15 (1%), −2.88 (5%) and −2.74 (10%).
Table 3
Parameter constancy test results
| Coefficient | Model 2 | Model 3 |
|---|---|---|
| χ2 | 694.57 | 588.93 |
| (0.000) | (0.000) |
[i] The values in parentheses refer to p-values.
Table 4
Random coefficient regression model coefficients for Model 1
| Country | Czechia | Hungary | Poland | Slovakia | ||||
|---|---|---|---|---|---|---|---|---|
| GL_HT | −0.0704 | (0.404) | 0.1050 | (0.563) | 1.2351*** | (0.249) | 1.289*** | (0.5005) |
| GL_MT | 0.2208 | (0.579) | 0.0689 | (0.512) | −1.4072 | (1.283) | −0.279 | (0.241) |
| GL_LT | 1.3453 | (1.066) | 1.7504* | (0.947) | 0.1776 | (0.794) | −0.511 | (0.643) |
| FDI | −0.0087 | (0.006) | 0.0001 | (0.0004) | 0.0016 | (0.0098) | 0.009 | (0.0064) |
| LogImport | −1.352* | (0.694) | −1.251* | (0.694) | −1.2075* | (0.698) | −2.827*** | (0.673) |
| LogRD | 0.6005 | (0.454) | 0.1768 | (0.553) | 1.228** | (0.533) | −0.109 | (0.287) |
| LogResearcher | 0.841*** | (0.144) | 1.1051*** | (0.183) | −0.4478** | (0.215) | 1.776*** | (0.307) |
[i] ***, ** and * refer to 1%, 5%, and 10% significant levels, respectively. The values in parentheses correspond to standard errors.
Table 5
Random coefficient regression model coefficients for Model 2
| Czechia | Hungary | Poland | Slovakia | |||||
|---|---|---|---|---|---|---|---|---|
| VERTHQ_HT | 1.195*** | (0.331) | 1.484** | (0.649) | 2.543*** | (0.599) | 1.5311*** | (0.280) |
| VERTHQ_MT | 0.065 | (0.4008) | 0.356 | (0.766) | −1.695** | (0.817) | −0.6512*** | (0.218) |
| VERTHQ_LT | −0.256 | (0.395) | −0.114 | (1.149) | −1.993* | (1.153) | −0.819*** | (0.312) |
| FDI | −0.002 | (0.004) | 0.000 | (0.0009) | −0.004 | (0.0125) | −0.006 | (0.003) |
| LogImport | −0.9514** | (0.446) | −1.657*** | (0.494) | −1.291*** | (0.491) | −2.544*** | (0.468) |
| LogResearcher | 0.4097*** | (0.135) | 0.9209*** | (0.313) | 0.300 | (0.327) | 1.708*** | (0.187) |
[i] ***, **, and * refer to 1%, 5%, and 10% significant levels, respectively. The values in parentheses correspond to standard errors.
Appendix A
Cross-section dependency test results
| Variables | CDLM1 | CDLM2 | LMadj |
|---|---|---|---|
| ECI | 106.5706 | 27.87753 | 27.76642 |
| (0.000) | (0.000) | (0.000) | |
| GL_HT | 19.33611 | 2.695103 | 2.583992 |
| (0.003) | (0.007) | (0.009) | |
| GL_MT | 48.55743 | 11.13057 | 11.01946 |
| (0.000) | (0.000) | (0.000) | |
| GL_LT | 34.05162 | 6.943106 | 6.831995 |
| (0.000) | (0.000) | (0.000) | |
| VERTHQ_HT | 53.55607 | 12.57355 | 12.46244 |
| (0.000) | (0.000) | (0.000) | |
| VERTHQ_MT | 10.1532 | 0.044226 | −0.066885 |
| (0.118) | (0.964) | (0.946) | |
| VERTHQ_LT | 14.61022 | 1.330855 | 1.219744 |
| (0.024) | (0.183) | (0.223) | |
| Fdi | 14.56701 | 1.318381 | 1.20727 |
| (0.024) | (0.187) | (0.227) | |
| LogImport | 30.15403 | 5.817966 | 5.706855 |
| (0.000) | (0.000) | (0.000) | |
| LogRD | 92.42095 | 23.79288 | 23.68177 |
| (0.000) | (0.000) | (0.000) | |
| LogResearcher | 67.20774 | 16.51445 | 16.40334 |
| (0.000) | (0.000) | (0.000) |
Appendix B
Correlation Matrices for Model 1 and Model 2
| Model 1 | |||||||
|---|---|---|---|---|---|---|---|
| GL_HT | GL_MT | GL_LT | Fdi | LogImport | LogRD | LogResearcher | |
| GL_HT | 1 | - | - | - | - | - | - |
| GL_MT | 0.7746 | 1 | - | - | - | - | - |
| GL_LT | 0.7667 | 0.7999 | 1 | - | - | - | - |
| Fdi | 0.0161 | −0.1464 | −0.1509 | 1 | - | - | - |
| LogImport | −0.3492 | −0.2576 | −0.1261 | −0.0871 | 1 | - | - |
| LogRD | 0.7107 | 0.4893 | 0.5864 | −0.0058 | −0.175 | 1 | - |
| LogResearcher | 0.0862 | 0.0952 | 0.2062 | −0.1306 | −0.0371 | 0.418 | 1 |
| Model 2 | |||||||
|---|---|---|---|---|---|---|---|
| VERTHQ_HT | VERTHQ_MT | VERTHQ_LT | Fdi | LogImport | LogRD | LogResearcher | |
| VERTHQ_HT | 1 | - | - | - | - | - | - |
| VERTHQ_MT | 0.5871 | 1 | - | - | - | - | - |
| VERTHQ_LT | 0.246 | 0.3713 | 1 | - | - | - | - |
| Fdi | 0.0903 | −0.0051 | −0.1073 | 1 | - | - | - |
| LogImport | −0.2745 | −0.0883 | 0.0355 | −0.0871 | 1 | - | - |
| LogRD | 0.864 | 0.7417 | 0.3039 | −0.0058 | −0.175 | 1 | - |
| LogResearcher | 0.4123 | 0.3267 | 0.6274 | −0.1306 | −0.0371 | 0.418 | 1 |
