# Construction of the Belt and Road Trade Cooperation Network from the Multi-Distances Perspective
## Variables and Model Expansion  
### Variables - Multiple Distances  
Based on cooperation benefits, the cooperation network formation theory expounds the principle of facilitation and complementarity of cooperation. Facilitation can reduce trade costs and the complementarity of the production factors constitutes an interdependent economic relationship. Both are beneficial to the two parties in terms of the acquisition of trade benefits. However, convenient exchanges and strong complementarity of factors can only provide basic preconditions for cooperation, but not conditions sufficient for cooperation. Therefore, considering the friendly relationships among countries is necessary [35]. The cooperation network formation theory, based on cooperation opportunities, expounds the cooperation principle of friendliness. Therefore, from the two aspects of cooperation benefits and cooperation opportunities, we chose metrics for geographic, factor endowment, cultural, and institutional distances from the perspective of multiple distances to measure the comprehensive distance indices between China and the Belt and Road countries. The four distance variables are specified as follows:  
1. Geographic Distance (_DIS_). Generally, the greater the geographic distance between two countries, the higher the trade risk and the transportation cost, which is not beneficial for the realization of trade cooperation between two countries. According to the distance calculation method introduced by [PERSON] [36], the formula of relative geographic distance is: \[DIS_{ijt}=GDP_{it}\ /GDP_{wt}\times DIS\] (1) where \(DIS_{ijt}\) is the relative geographic distance between country \(i\) and its trading partner country \(j\) in year \(t\), \(GDP_{it}\) denotes the gross domestic product (GDP) of country \(j\) in year \(t\), \(GDP_{wt}\) the world GDP in year \(t\), and \(DIS\) the absolute distance between the capital of country \(i\) and the capital of its trading partner country \(j\). The GDP data and the \(DIS\) data were separately obtained from the World Bank database and the Research and Expertise on the World Economy (CEPII) database. In this study, the geographic distance stands for relative geographic distance. 2. Factor Endowment Distance (DKL). When other conditions are constant, the stronger the factor complementarity between two countries, the greater the demand for each other's products, and the greater the possibility and necessity of cooperation [37]. In this study, we used the absolute value of the difference between the two economies' capital-to-labor ratios' logarithm to measure the factor endowment distance, in which the value of capital is the capital balance based on constant price. The figures were obtained from Penn World Table. As to the missing values for certain years, we interpolated the values by using the forecast function. 3. Cultural Distance (CD). Cultural distance is the distance between the export country and its trading partner country due to their differences in ideology, such as values or beliefs. Generally,the smaller the cultural distance between two countries, the stronger the sense of identity and trust, creating a greater possibility of trade cooperation. To calculate cultural distance, we used the cultural data provided by [PERSON] in the following four dimensions: Power Distance, Uncertainty Avoidance, Individualism-Collectivism, and Masculinity-Femininity.