Fig. 5: Parallel trend test.
From: Does the green patent pre-examination program reduce environmental pollution?
Figure 5 presents the results of the parallel trend tests according to the dynamic DID model. The variable current equals 1 for the year when the city is in the treatment group and 0 otherwise. The dependent variables in (a) and (b) of Fig. 5 are industrial sulfur dioxide and dust emissions, respectively. The circles represent the estimated values of \({\beta }_{t}\), and the dashed lines indicate the 95% confidence intervals.
