Administrative border effects in COVID-19 related mortality

Lombardy, the first region in Italy to be hit by COVID-19 and one of the first in Western countries, was in the spotlight during the first wave of the pandemic in 2020 due to its high mortality rates. Simple regional comparisons are, however, hampered by potentially unobservable variables affecting mortality, such as the virus spread. To address this 'unobserved heterogeneity' concern, we adopt a Difference in Geographic Regression Discontinuity Design (DiD-GRDD), which compares 2020 vs. 2017-2019 excess mortality in Lombardy's municipalities close to the administrative borders with neighbouring municipalities in other regions. Our study documents a one to two percentage point higher excess mortality in Lombardy limited to the oldest age group (81+). An exploratory mediation analysis points to the management of nursing homes during the pandemic as a possible critical factor explaining higher mortality in Lombardy.