A while ago, I started getting messages that my computer was running out of memory. I put off doing anything about it -- cleaning up a decade's worth of files did not sound like a fun task. But eventually I took a look, sorted files by size, and came to a lovely discovery. There were a few large files -- some video attachment to an email someone sent me three years ago, stuff like that. After I deleted 10 or 20 of these, all of a sudden there was lots of space! The rest of my computer remains a Marie Kondo nightmare.
Every distribution has fat tails. And if you need to do something about it, spend all your time on the tail events and don't bother with the small stuff.
That lesson, of course applies to stopping the spread of the corona virus. Stopping the negligible possibility that a hiker passes it to another hiker out on a (now closed) trail in the Santa Cruz mountains is beyond pointless. Stopping the tiny probability that a worker passes it to another worker in a thoughtfully structured high value business is equally pointless, and vastly more costly.
What do we know about the fat tail? Not as much as we should. Jonathan Kay's lovely Quillette essay on super spreader events covers a lot. (HT Marginal Revolution).
Jonathan points out that our scientists still don't reallhy know whether Covid-19 is spread primarily by large "ballistic" droplets, small persistent aerosol droplets, or contact with surfaces where droplets have landed. They don't know what kind of activities lead to spread. He investigated super spreader events to try to figure out. Jonathan put together all the information he could find on known Covid-19 super spreader events. He found 54, with details on 38. A bit more data collection and research effort on this crucial question would seem worthwhile.
I have a different goal -- what are the activities that we can reduce with greatest effect on the disease, and least economic cost, and within the everyday more apparent limitations of our political and government apparatus?
Like others (see Arnold Kling for example) I'm starting to despair of a way out. We will not have a vaccine for a long time, and kill the economy till the vaccine comes is not an option. Bend the curve, followed by vigorous test, trace and isolate would be possible, but I doubt the US, has the institutional capacity or political will for trace and isolate once we eventually get test to work. I cannot imagine our authorities imposing life in Wuhan (another MR HT). Paul Romer has articulately advocated a big push for widespread testing, notably by relaxing regulations (university labs not allowed to conduct tests, for example). Paul notes correctly that it's worth spending hundreds of billions of dollars on testing to save trillions of dollars of economic and fiscal damage. If we could test everyone every day, and get most of the positives to stay home, the virus would quickly peter out. But I'm dubious our government is capable of even this. Let it rip, argue many others, and wait for herd immunity. But I don't think our governments can do that either, as Boris Johnson found out.
Our governments can, however, come up with lists of banned activities. So let those lists have just a little more common sense. Let the lists of banned activities 1) focus on the tail of super spreader events 2) consider the economic damage vs. public health benefit.
The bottom line I get from Jonathan: It looks like the biggest transmission danger is large droplets exchanged by people talking loudly in large gatherings, in closed quarters, and where many different people interact. Yes, it may be transmitted in other ways, but this is the fat tail, and start with the fat tail. The even greater news: practically no GDP is lost if you ban the super spreading activities on his list.
However the rhetoric needs to change. Right now the calls are for "relax social distancing." This is exactly wrong. Keep social distancing, but relax economic prohibitions. The challenge is that our regulatory state finds it much easier to shut down business -- at tremendous economic cost -- than birthday parties.
Epidemiologists know about fat tails “20% of the individuals within any given population are thought to contribute at least 80% to the transmission potential” of previous infectious diseases.
Also from here (again HT Marginal Revolution)
We identified only a single outbreak in an outdoor environment, which involved two cases. Conclusions: All identified outbreaks of three or more cases occurred in an indoor environment, which confirms that sharing indoor space is a major SARS-CoV-2 infection risk.An added observation: Fat tails of superspreader events helps to explain why the virus seems to spread quickly in some places and not in others. 2,4, 8, 16, 32, 64, actually takes a while to get to 10,000. 2, 124, 256 from an early super spread event gets you there much faster.
Many of the early SSEs, in fact, centered on weddings, birthday parties, and other events.The joy of life, but nearly zero GDP.
In fact, the truly remarkable trend that jumped off my spreadsheet has nothing to do with the sort of people involved in these SSEs, but rather the extraordinarily narrow range of underlying activities.Great news. We don't have to find dangerous people, just ban a small list of easily identifiable activities.
Of the 54 SSEs on my list for which the underlying activities were identified, no fewer than nine were linked to religious services or missionary work.Nearly zero GDP.
Nineteen of the SSEs—about one-third—involved parties or liquor-fueled mass attendance festivals of one kind or another, including (as with the examples cited above) celebrations of weddings, engagements and birthdays.
Five of the SSEs involved funerals.
Six of the SSEs involved face-to-face business networkingFinally some GDP, but easy to stop. We already have.
These parties, funerals, religious meet-ups and business networking sessions all seem to have involved the same type of behaviour: extended, close-range, face-to-face conversation—typically in crowded, socially animated spaces. This includes the many people infected by a bartender while being served at a raucous après ski venue in Austria, and party guests in Brazil greeting “each other with two kisses on the cheek [a local custom], hugs and handshakes.” The funerals in question are generally described as highly intimate and congested scenes of grieving among close friends and relatives. In the case of the SSE funeral in Albany, Georgia that devastated the local population, “people wiped tears away, and embraced, and blew their noses, and belted out hymns.
With few exceptions, almost all of the SSEs took place indoors, where people tend to pack closer together in social situations, and where ventilation is poorer. (It is notable, for instance, that the notorious outbreak at an Austrian ski resort is connected to a bartender and not, say, a lift operator.)
. At a February 15 festival in Gangelt, a town in Germany’s tiny Heinsberg district, “beer and wine flowed aplenty as approximately 350 adults in fancy dress locked arms on long wooden benches and swayed to the rhythm of music provided by a live band. During an interval in the programme, guests got up to mingle with friends and relatives at other tables, greeting each other as Rhineland tradition commands, with a bützchen, or peck on the cheek.” Since that time, more than 40 Germans from the Heinsberg district have died. It’s been called “Germany’s Wuhan.”
The virus makes no distinction according to creed, but does seem to prey on physically intimate congregations that feature some combination of mass participation, folk proselytizing and spontaneous, emotionally charged expressions of devotion. I
Three of the SSEs—in Japan, Skagit County, WA, and Singapore—involved concert-goers and singing groups belting out tunes together over a period of hours. ...
Another SSE involved a group of Canadian doctors engaged in a day of recreational curling. This is a sport that involves hyperventilating participants frenetically sweeping the ice with brooms while their faces are positioned inches apart, sometimes changing partners—an ideal climate for Flüggian infection. Indeed, this partner-swapping aspect of the activity seems to be a common feature of many suspected SSEs, such as square-dancing parties.
Four of the SSEs were outbreaks at meat-processing plants, in which “gut snatchers” and other densely packed workers must communicate with one another amidst the ear-piercing shriek of industrial machinery. ... high levels of noise do seem to be a common feature of SSEs, as such environments force conversationalists to speak at extremely close range.Some GDP here, but a work environment that one could easily fix.
When do COVID-19 SSEs happen? Based on the list I’ve assembled, the short answer is: Wherever and whenever people are up in each other’s faces, laughing, shouting, cheering, sobbing, singing, greeting, and praying.We can let a lot of GDP get going while respecting these rules.
What isnotdangerous is just as informative to policy as whatis dangerous
It’s worth scanning all the myriad forms of common human activity that aren’t represented among these listed SSEs: watching movies in a theater, being on a train or bus, attending theater, opera, or symphony...These are activities where people often find themselves surrounded by strangers in densely packed rooms—as with all those above-described SSEs—but, crucially, where attendees also are expected to sit still and talk in hushed tones.
The world’s untold thousands of white-collar cubicle farms don’t seem to be generating abundant COVID-19 SSEsThere is a lot of GDP there!
Moreover, I had trouble finding any SSEs that originated in university classrooms, which one would expect to be massive engines of infection if COVID-19 could be transmitted easily through airborne small-droplet diffusion.Universities -- which will face a huge question whether to reopen in the fall, might want to send their research doctors out to find the answer to this question now.
On the other hand, universities might be a microcosm of my above regulatory conundrum. A visitor from, China, say, visiting an average American college, might miss the fact that students are supposed to go to classes at all, and think it's one grand alcohol-fueled bacchanalia. Keeping "social" distance in the dorms and frats will be the university's problem, not the classroom. Good luck with that.
It’s similarly notable that airplanes don’t seem to be common sites for known SSEs, notwithstanding the sardine-like manner in which airlines transport us and the ample opportunity that the industry’s bureaucracy offers for contact tracing. Yes, New Zealand has one cluster that’s based around an infected but asymptomatic flight attendant. But the many known infections he caused took place at a wedding reception, not in an airplane. This flight attendant was running what was, in effect, an unintended experiment, with the passengers on board his aircraft playing the role of control group. And the results offer a microcosm of the nature of SSEs as a whole.Airlines might want to scream this from the rooftops. Given a huge bailout, the government might want to spend some time and money figuring out just how dangerous an airplane is.
The bottom line I read from Jonathan: Dear Fellow Citizens: Go out. Start up businesses. And shut up!
Update: thanks to commenters for typos.