I have come across two research approaches: 1) studying the spatial correlations of services at several time points and then observing changes in the results at those time points; 2) calculating changes in service quantities over a period of time and using these changes for correlation analysis.
Personally, I lean towards the latter because I believe that trade-offs and synergies are descriptions of processes. I cannot understand the mechanism behind the former approach because analyzing spatial variations at different time snapshots does not necessarily imply the existence of trade-offs or synergies among services, despite the fact that this approach is more commonly used in existing research.
What's your opinion?