  This study quantifies the economic effect of a possible lockdown of Tokyo to
prevent spread of COVID-19. The negative effect of the lockdown may propagate
to other regions through supply chains because of shortage of supply and
demand. Applying an agent-based model to the actual supply chains of nearly 1.6
million firms in Japan, we simulate what would happen to production activities
outside Tokyo when production activities that are not essential to citizens'
survival in Tokyo were shut down for a certain period. We find that when Tokyo
is locked down for a month, the indirect effect on other regions would be twice
as large as the direct effect on Tokyo, leading to a total production loss of
27 trillion yen in Japan, or 5.3% of its annual GDP. Although the production
shut down in Tokyo accounts for 21% of the total production in Japan, the
lockdown would result in a reduction of the daily production in Japan by 86% in
a month.
