I would first point out that your prognostications assume ignorance on the part of the populace.
I don’t know how well socialized the information was in 1918, that the second wave could be worse than the first, or it if was at all. But what I do know is that today, we communicate around the world at lightspeed, not by primitive radio and telegraph; and that 100% of the political leadership in the world will be laser-focused on indications that a 2nd wave is nigh. So, if a 2nd wave presents itself, I expect we’ll go back into lockdown in heartbeat.
But, this time, the economic impact of lockdown will not be as great. First, we’ll have SOME individual in the population who carry immunity; second, we’ll already know the drill on how to be productive in a non office environment. An economic downturn would of course ensue, but not to the extreme that we are experiencing at present.
Secondly, several commentators have pointed out that the Spanish Flu was all told much more deadly than COVID19, and that comparisons are better made with the Asian Flu of 1957–58. This also had a second wave, but the second wave was muted compared to the first.
But, to answer your question……the sane trader is writing off 2020 and perhaps 2021, and asking the question, “what is the value of stock X when normal times do return?” Or, perhaps a better phrasing might be, “Assuming COVID has no permanent impact on earnings, what’s the value of stock X?”
Step one is to sort industry groups into two groups. Group A are stocks which should see no long term impact from COVID; their core business will pick up again. Group B are stocks which COULD see long term impact — — casual dining restaurants may take a long time to return to some semblance of normal.
And if you divide stocks that way, Group “A” contains a lot of bargains right now, assuming you’re patient enough to ride out the volatility.