Here’s a good paper that studies returns going back to 1920 to see how buying a country, company, or industry that has had a decline of 60% or more does for the next 3 years.
Basically it’s saying there’s validity to Warren Buffet’s phrase “be greedy when others are fearful and fearful when others are greedy.”
Of course, there were notable exceptions to the rule, but an interesting article and study nonetheless.