Not even during the Great Depression and World War II did the bulk of economic activity literally shut down, as it has in China, the United States, and Europe today. The best-case scenario would be a downturn that is more severe than the GFC (in terms of reduced cumulative global output) but shorter-lived, allowing for a return to positive growth by the fourth quarter of this year. In that case, markets would start to recover when the light at the end of the tunnel appears.

But the best-case scenario assumes several conditions. First, the US, Europe, and other heavily affected economies would need to roll out widespread COVID-19 testing, tracing, and treatment measures, enforced quarantines, and a full-scale lockdown of the type that China has implemented. And, because it could take 18 months for a vaccine to be developed and produced at scale, antivirals and other therapeutics will need to be deployed on a massive scale…

Third, governments need to deploy massive fiscal stimulus, including through “helicopter drops” of direct cash disbursements to households. Given the size of the economic shock, fiscal deficits in advanced economies will need to increase from 2-3% of GDP to around 10% or more. Only central governments have balance sheets large and strong enough to prevent the private sector’s collapse.