Table 6.

Robustness tests on Covid-19 cases and school opening.

	Serial Time=5 days	IHS	Cases over Population	Interaction term
	(1)	(2)	(3)	(4)
School opening (2nd lag)	0.019***	0.026***	0.024***	0.026***
	(0.001)	(0.001)	(0.001)	(0.001)
School opening (2nd lag) X 2nd lag dependent				−0.002
				(0.005)
Covid-19 (ln, 2nd lag)	−0.785***	−0.609***	−0.789***	−0.788***
	(0.005)	(0.004)	(0.005)	(0.005)
Covid-19 (ln, 3d lag)	0.057***	0.008***	0.011***	0.011***
	(0.003)	(0.002)	(0.003)	(0.003)
Covid-19 (ln, 4th lag)	0.022***	−0.016***	−0.021***	−0.020***
	(0.003)	(0.002)	(0.003)	(0.003)
Covid-19 (change ln lag)	−0.881***	−0.669***	−0.865***	−0.863***
	(0.003)	(0.003)	(0.004)	(0.005)
Time dummies	Y	Y	Y	Y
Census areas fixed effects	Y	Y	Y	Y
Observations	796,416	530,944	505,856	530,944
R${}^2$ within	0.44	0.43	0.43	0.43
Number of Census areas	33,184	33,184	31,616	33,184

All regressions are weighted by propensity scores. ***, **, and * denote significance at 1%, 5%, and 10%, respectively. Standard errors are clustered at census area level. The dependent variables are the natural log of the Covid-19 cases measured with a serial time of 5 days (column 1), the Inverse Hyperbolic Sine Transformation (IHS) of the Covid-19 cases (column 2); the share of Covid-19 cases over the census area population in 2011 (column 3); and the log of the Covid-19 cases (column 4).