**Appendix A**

We plotted the Kilian index according to the data from the Lutz Kilian website, which showed the monthly index of the global real economic activity. This figure shows that fluctuations in global real economic activity are consistent with the anecdotal evidence. It is commonly accepted that when war breaks out and crises or threats occur, trade uncertainty rises and these events damage global economic activity.

**Figure A1.** The Kilian Index. **Note** This figure illustrates time-changing trend of the Kilian Index [15] from Jan. 1968 to Jun. 2019.
