Table 2.

Average change in PM_2.5 concentration during mitigation periods between 2020 and the comparable dates for 2017–2019, by state and the District, based on difference-in-difference approach.

State/district⁎	No. of counties included/total No. counties	Mitigation vs baseline period for 2020	Mitigation vs baseline period for 2017–2019	Difference in difference
California	41/58	−4.03	0.18	−4.20
Connecticut	5/8	−2.97	−1.72	−1.25
Florida	28/67	0.44	0.94	−0.50
Maryland	11/24	−1.26	−1.01	−0.25
Massachusetts	11/14	−2.06	−1.47	−0.59
New Jersey	11/21	−1.94	−1.24	−0.70
New York	18/62	−2.27	−1.70	−0.57
Pennsylvania	28/67	−1.48	−1.49	0.01
Texas	29/254	2.91	0.78	2.13
Washington state	30/39	−0.11	−1.28	1.17
Washington, D.C.	1/1	−0.84	−0.45	−0.39

^⁎States represent the portion of states with monitoring networks. PM_2.5 levels are population weighted.