The math on the cost of infecting people
What if you give somebody a disease that harms them? It is legal to sue over this, and to have wrongful death lawsuits by the survivors. Wrongful death lawsuits, according to one recent North Carolina study, fetched about $1.4M on average, though they are going to vary a lot. They combine lost income with pain and suffering by the survivors. While wrongful death lawsuits are done after-the-fact, if you considered them taking place before the death (as they sometimes did with AIDS.) Indeed, the general statistical value put on a human life by policymakers is around $10M, no matter what the age.
Cost of deaths
Costing human lives is always complex, particularly when you describe hypothetical activities which will take them. For many people, the amount of money you would need to pay them to get advance consent to risk their lives is much higher than these statistical values. Some people would accept $100,000 to let you put their life 1% at risk, others would have a higher price. Some are rich enough that there is no amount they would accept.
But to make it simple, let's work on the lower end of the spectrum at $1M, and let's use today's commonly estimated infection fatality rate of 1% -- lower than the 3.5% that the WHO published at the time that policymakers were deciding lockdowns.
This means that infecting somebody should have a mean cost of at least $10,000, just for the death risk. However, infecting them also puts them at much higher risk for at least 2 painful weeks of downtime, and loss of work, or in cases with light symptoms, just the 2 weeks of isolation and loss of work. You need to add about $5,000 for that. Some decent fraction of those infected might need hospitalization, which could cost tens of thousands extra -- I have not factored this in, and in the current world this is paid by health insurance, but in this hypothetical world the insurance company would go after the infector for the costs.
Wrongful death suits don't include money to make up for the death itself, as that can't be remedied and the dead can't sue. Criminal law deals with that. The fatally ill can sue, but not in a way as to get remedy before they die.
Cost of downstream infections
The problem is that infecting one person isn't where it ends. Your infectee is going to spread secondary infections, and they are going to spread more, and so on, and so on, until the outbreak ends.
You are certainly at least partly responsible for those they infect. One can argue it would not have happened at all without you. Some of them will also do things they shouldn't, and bear some responsibility, and share the liability with you. Each case would be different -- the symptomatic infectee who went to a cuddle party bears a lot more share of responsibility than the cautious one who sheltered at home but touched a handrail while shopping. As before though, we want to figure a mean, which will be more the result of policy and precedent. For a simple model, let's consider a 50-50 split, with you being responsible for 1/2 of the costs of those you infect, and your infector responsible for the rest. As such, you are responsible as well for 25% of the costs of those infected by your infectees and so on.
Now you can project a number. Estimates for the R0 of SARS-Cov2 range from around 3 to 6 in a non-locked-down world. Let's go with the lower bound of 3.
Put it all together and the average infected person will infect 3, with a cost of $15,000 or a total of $45,000 from just those three. However, they will infect others. How many is hard to calculate. If you are "patient 0" at the start of an epidemic, then you will be responsible for the whole population. The number downstream from you is going to depend on what fraction of the population is left to be infected (today that's well over 90%) and how many other people are, like you, not social distancing.
If there are 10,000 not social distancing infected in a country of 300M people like the USA, and it goes on until herd immunity with 250M infected and 2.5M dead, then on an even basis, each of the 10,000 will, on average, be responsible for 25,000 infections and 250 fatalities. (This is a great oversimplification because some of those who are keeping locked down will still infect a few, but we can use it for this back of envelope analysis.) That's about 8 or 9 generations at R0 of 3.
Here's a breakdown of how that works. You will infect 3 people. Each of them is owed $15,000, for a total of $45,000. But half of that -- $22,500 is owed by the person who infected you. (Who will in turn be owed have of that by their infector.)
Your 3 infectees will infect 3 each, for 9 grand-infectees of yours. Again, they each deserve $15K, but you are responsible for only 1/4 of that, adding on average $34K. Next generation has 27 infectees for which you owe only 1/8th and so on. By the time we get to generation 8, there are 6,500 infectees but you owe only 1/256th of their total liability -- about $400K. It keeps growing in this exponential way until herd immunity (or a lockdown) slows the growth.
The last variable we must add is the probability that, if you go out and socialize, you will get infected. Most estimates suggest that's pretty high in a non-locked down world. The only question is whether it happens sooner (when you will then contribute to the infection of many) or later, as the herd immunity approaches. But if you accept a 5% chance of getting infected fairly early on, your expected cost just for going outside runs about $50,000. And about 9 manslaughter charges on average. But with that number, it means the risk you take by being an early-adopter of non-locked down life is about $50,000, and about 9 possible homicide/manslaughter chargers.
It's not like you step outside and it costs you $50K and a homicide rap. Some poeple would go out and infect nobody, or do it very late. Others would infect and kill an above average number of people. It would be a big gamble, though of course it is one you control since you can control how much you socialize. Protestors want to socialize almost like 2019, going to restaurants, movies, jobs, sporting events. The real cost you would end up responsible for would range from nothing to many millions.
When you have that much range of risk, the answer is to buy insurance, at least for the financial risk. But the insurance companies are going to want a premium of probably double the average liability -- which is to say, in this calculation, of about $100,000.
Are you ready to pay that premium? Or just take the risk of losing the $millions? Do you even have the $millions to pay? Of course, even if you can afford that, if the criminal charges come to bear, not even a billionaire can afford them.
Which means, you're going to lock down, even if it means losing a lot of money. Even without the jail time. Sure, you will argue that those people who died would have got it some other way if not via you, but it will be you that did it. And with all the press, nobody can argue you didn't know better. Especially if you were in a protest march, defying the advice to lockdown.
You can play with the numbers. As R0 goes up, your liability risk becomes much higher if you get infected early, and lower if you do it later. If R0 hits the magic number of 2 (which is to say, the reciprocal of the portion of the liability passed on to the person who infected you) the cost is no longer exponential and becomes flat, but still equal to about $300,000 if you get infected and a more tolerable $15,000 if you take a 5% risk of getting infected. The risk of killing is still very high.
If your infector takes less than half the liability for downstream infections, you can slow it down. If they take more than half (which many would argue is reasonable because the infections don't happen without them,) it speeds up.
The core reality is this -- an exponential number of people get infected (or dead) thanks to you, and if you take your responsibility for it in any serious way, the cost is immense. So high that you won't need any law to tell you to lock down, to close your business, to abandon your job, and to shelter in place.
Get R0 down (with a lockdown) and suddenly the disease dies out with time rather than growing to herd immunity. Your cost is much more reasonable. In addition, if you did everything reasonable to avoid infecting others, chances are you would not be guilty of negligent homicide.
Homicide and manslaughter, however, are very different from civil liability. They can't are not "split up" so that if your secondary infectee dies, you and the intermediary each get charged with "half a homicide." When two people participate in a homicide, they both get a homicide charge, even if one is much more culpable than the other. (There can also be conspiracy charges for groups.) The concept of 8 people in a chain being responsible for a homicide is of course untested. Certainly in a deliberate homicide (where a client pays a mob boss for a hit, and the boss gives it to a subordinate who gives it to a hit man) all would be guilty of murder-for-hire and probably consiracy. It's clear clear when the killing is negligent rather than intentional, or not even willful. (Those who are not social distancing today, however, are aware they are not doing it and that it is a risky activity for them and others.)
Some may wonder, "But Don't I get a payment from my own infector to balance this?" You do, but that payment is not to balance you for that. Rather it would or should be to compensate for the actual hardships you got for being infected. If you got no symptoms, it would only cover your cost of quarantine -- if you knew to do that. If you got hospitalized you would get more, but you suffered a terrible cost, so it's not a profit for you, unless there are punitive damages added.
This number gets further complication if some liability is given to those who facilitated the breeding and transmission of the disease, namely those who operated venues and events where people congregated, particularly when they did so knowing the risk. If I get Covid from somebody who attended a tightly packed church in spite of all warnings of the risk of that, one can argue that my infector, their infector and the church all play a role and have a share of liability.
It's hard to say what share of liability they would get. If it's a very large share it actually would diminish the cost to individuals. But it does not have to be a very large share before it scares the venues and events, and their insurance companies. This is particularly true in the world of deep pocket lawsuits, where such parties are more prone to being sued, though I am hypothesizing a world where we can actually find all the liable parties. Even in that world, the deep pocketed parties would pay more because some of the individuals would not have financial means to pay the remedy.
As such, you would find that most businesses, venues and events would be unable to get insurance of any kind if they didn't shut down. If they could buy insurance that excluded Covid liability they could afford that, but they would have to face that liability on themselves -- possibly low if there is minimal infection at their event, but quite possibly catastrophic and business-ending. They'll shut down.