Fig. 5
From: North Korea’s COVID-19 policy dilemma: epidemic prevention conflicting with trade
Night-time light response to the border closure by group. Note: The vertical dotted line at number 4 corresponds to January 2020, when border closures began. Each point represents a DID estimate. This study used the cluster standard error at the cell-level. The pre-trend coefficients of Chinese border cities were far from zero and gradually increased. They seemed to have increased as trade with China continued to increase from 2018 until the border closure owing to strengthened US sanctions against North Korea and China’s easing of trade with North Korea [41]. The DID estimates are in Table 4 in Appendix