## 3 Concept, Classification, and Data Sources of Digital Service Trade
### Association Analysis  
Correlation reflects the stability and vulnerability of the interconnections between various economies in the network. In social network analysis, three indicators are generally used to measure the overall network connectivity: network relatedness, network rank, and network efficiency. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Proportion of Intra Sector** & \multicolumn{3}{c}{**The Ratio of Digital Service Trade Exports and Imports**} \\
**Trade Relations** & \multicolumn{3}{c}{**Between This Sector and Other Sectors**} \\ \(\mathbf{I_{k,r}}\)\(\mathbf{I_{k,i}}\)\(\mathbf{\geq 1}\) & \(\mathbf{I_{k,r}}\)\(\mathbf{<1}\) \\ \hline \(\mathbf{I_{k}}\)\(\mathbf{\Big{/}}\)\(\mathbf{I_{k,i}}\)\(\mathbf{\geq(nk-1)}\)\(\mathbf{\Big{/}}\)\(\mathbf{(n-1)}\) & bidirectional plate & introverted plate \\ \(\mathbf{I_{k,r}}\)\(\mathbf{\Big{/}}\)\(\mathbf{I_{k,l}}\)\(\mathbf{<(nk-1)}\)\(\mathbf{\Big{/}}\)\(\mathbf{(n-1)}\) & outward oriented sector & isolated plate \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Classification standards for digital service trade network blocks. \begin{table}
\begin{tabular}{c c c c c} \hline \hline  & \multicolumn{4}{c}{**2006**} \\ \hline  & **First Section** & **Second Section** & **Third Section** & **Fourth Section** \\ \hline First section & 1 & 1 & 0 & 0 \\ Second section & 1 & 0 & 1 & 0 \\ Third section & 0 & 1 & 0 & 0 \\ Fourth section & 0 & 0 & 0 & 0 \\ \hline \hline  & \multicolumn{4}{c}{**2021**} \\ \hline  & **First Section** & **Second Section** & **Third Section** & **Fourth Section** \\ \hline First section & 1 & 1 & 1 & 0 \\ Second section & 1 & 1 & 1 & 0 \\ Third section & 1 & 1 & 0 & 0 \\ Fourth section & 0 & 0 & 0 & 0 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Overall digital services trade network matrix of RCEP member countries in 2006 and 2021. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Section** & **2006** & **2021** \\ \hline First section & China, Japan, South Korea, Australia, Singapore, Thailand & China, Japan, South Korea, Australia, Malaysia, Thailand, Singapore \\ \hline Second section & Philippines, Malaysia, Vietnam & Philippines, Indonesia \\ \hline Third section & Indonesia, New Zealand & Cambodia, Laos, New Zealand, Vietnam \\ \hline Fourth section & Laos, Brunei, Myanmar, Cambodia & Myanmar, Brunei \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Overall delineation of digital service trade network sectors among RCEP member countries in 2006 and 2021. As shown in Figure 5, in 2006, the correlation index of the overall trade network and various sub-industry trade networks of RCEP member countries was between 0.85 and 0.90 and then showed varying degrees of increase in different years. The correlation index of the overall trade network remained at 0.87 from 2006 to 2010, reaching 1 for the first time in 2011 and remaining stable until 2021. The correlation index between insurance and pension services and financial service also reached 1 in 2011 and has remained at this value ever since. The correlation index of personal entertainment services exceeded 0.92 in 2021 and reached its maximum value of 1 in 2012, which continued until 2021. The correlation index of intellectual property services, communication, computer, and information technology (ICT) services, and other business services increased to 1 in 2013 and remained unchanged until 2021. This reflects the continuous improvement of the overall network of digital service trade and the trade network of segmented industries among RCEP member countries. The digital service trade between countries is becoming increasingly close, gradually forming a more stable network structure. The network hierarchy reflects the hierarchical structure between network nodes. The lower the hierarchy, the lower the dependence of a node on other nodes and the more stable the network structure. Conversely, the higher the hierarchy, the easier it is for nodes to be 'controlled' by other nodes, which is not conducive to the stability of the network structure.