Washington State and Maine also experience seasonal forcing. They started requiring masks in June & July. From FT.com [1], here are the number of new confirme

Washington State and Maine also experience seasonal forcing. They started requiring masks in June & July. From FT.com [1], here are the number of new confirmed Covid-19 cases, per million residents, averaged over the last 7 days: - Maine: 130 - Washington State: 230 - Idaho: 740 - Montana: 1000 - South Dakota: 1600 From this data, I conclude that mask use is effective at reducing the spread of covid-19. [1] https://ig.ft.com/coronavirus-chart/?areas=eur&areas=usa&areas=bra&areas=gbr&areasRegional=usme&areasRegional=usmn&areasRegional=ussd&areasRegional=uswa&areasRegional=usid&areasRegional=usmt&byDate=1&cumulative=0&logScale=0&perMillion=1&values=cases https://ig.ft.com/coronavirus-chart/?areas=eur&areas=usa&are...