Table 1 Effects of the government policies on NO2 TVCD.

NO2 TVCD is based on OMI. We use a fixed-effects model (Eqs. 1 to 3) with the first case announced and lockdown coded as binary indicator variables. We control for the average 2015–2019 OMI NO2 TVCDs to adjust for seasonal variation and include provinces’ fixed-effects to adjust for geographical variation. The “Constant” term is the average province fixed-effect used as a baseline to compare the relative effect of the policy interventions. All SEs (shown in parentheses) are clustered at the province level.

Outcome variable
NO2 TVCD (1015 molecules/cm2)
First case
announced in
province, β
Lockdown of
province, λ
Average NO2
2015–2019, δ
Constant, α4.8474.4404.897
Number of
Adjusted R20.5390.5400.544

*P < 0.05.

**P < 0.01.

***P < 0.001.