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. Author manuscript; available in PMC: 2020 Mar 18.
Published in final edited form as: Am Econ Rev. 2019 Dec;109(12):4178–4219. doi: 10.1257/aer.20180279

Figure 1. Trends in PM 2.5 Air Pollution and Monitoring, 1999–2013.

Figure 1.

Note: The figure displays annual county means for PM 2.5 concentration (panel A) and the nationwide total number of PM 2.5 monitors (panel B).