The problem is that the externally driven factor can cause systemic issues. Having 25% retail & restaurant sales for a year will wipe out savings for a significant portion of the world. Most people will be fearful of spending for a long, long while.
This is particularly acute since the American economy derives a big part of its drive from consumer spending, unlike other economies that may be more producer or infrastructure driven.
Airlines are another one. The market expects domestic travel bans Soon (tm), forecast for United is revenue is down 9% this quarter and 95% next quarter.
I'll be curious how this affects package delivery, personally. A lot of 2-day shipping flies on those passenger planes. If anything shipping volume will be up but there will be fewer planes to put it on.
