Effectiveness of stay-in-place-orders during COVID-19 pandemic: Evidence from US border counties.

Recent studies on US counties, with varying effect sizes, show that stay-in-place-orders (SIPOs) are associated with a decline in new COVID-19 cases. Our estimation approach relies on county-pairs across state-borders where one state has SIPO whereas the other state does not, controls for matched county-pair fixed effects and day of observation fixed-effects. The county-pair sample from southern, mid-western, and mountain region states (from March 1, 2020 to April 25, 2020) shows that daily COVID-19 incidence case growth rate is 1.994 percentage points lower for counties in SIPO states relative to those bordering in non-SIPO states. Specifically, we find SIPO reduced daily growth rates by 1.97, 2.14, 2.03, and 2.27 percentage points after 1 to 5 days, 6 to 10 days, 11 to 15 days, and 16 to 20 days, respectively. Our effect sizes are much smaller than in the previous studies with the caveat that states in the northeast and on the west coast could not be included in the border county-pair specification. We find limited evidence of heterogeneous effects in counties with a higher population density, percentage of black or Hispanic residents, proportion of population over 65 years, and social association rates in a county. Nor do we find evidence of meaningful differences in effects of SIPO by county Gini index, unemployment, or GDP. The results of this study could further inform policymakers in making decisions on SIPO extensions or lifting of such orders.