Pandemics and persistent heterogeneity

It has become increasingly clear that the COVID-19 epidemic is characterized by overdispersion whereby the majority of the transmission is driven by a minority of infected individuals. Such a strong departure from the homogeneity assumptions of traditional well-mixed compartment model is usually hypothesized to be the result of short-term super-spreader events, such as individual’s extreme rate of virus shedding at the peak of infectivity while attending a large gathering without appropriate mitigation. However, heterogeneity can also arise through long-term, or persistent variations in individual susceptibility or infectivity. Here, we show how to incorporate persistent heterogeneity into a wide class of epidemiological models, and derive a non-linear dependence of the effective reproduction number R_e on the susceptible population fraction S. Persistent heterogeneity has three important consequences compared to the effects of overdispersion: (1) It results in a major modification of the early epidemic dynamics; (2) It significantly suppresses the herd immunity threshold; (3) It significantly reduces the final size of the epidemic. We estimate social and biological contributions to persistent heterogeneity using data on real-life face-to-face contact networks and age variation of the incidence rate during the COVID-19 epidemic, and show that empirical data from the COVID-19 epidemic in New York City (NYC) and Chicago and all 50 US states provide a consistent characterization of the level of persistent heterogeneity. Our estimates suggest that the hardest-hit areas, such as NYC, are close to the persistent heterogeneity herd immunity threshold following the first wave of the epidemic, thereby limiting the spread of infection to other regions during a potential second wave of the epidemic. Our work implies that general considerations of persistent heterogeneity in addition to overdispersion act to limit the scale of pandemics.

Here is the full paper by Alexei Tkachenko, et.al., via the excellent Alan Goldhammer.  These models are looking much better than the ones that were more popular in the earlier months of the pandemic (yes, yes I know epidemiologists have been studying heterogeneity for a long time, etc.).

Emergent Ventures India, second cohort of winners

Praveen Mishra

Praveen Mishra when he was 16 started the Power of Youth, a non-profit aimed at empowering rural students by giving them mentorship and conducting competitions to highlight their potential. He since has been building a ‘YouTube of e-commerce’. He is the founder of ByBuy, an omni-channel retail platform, and he received his EV grant to help with this launch.

Akash Bhatia and Puru Botla

Akash and Puru are the co-founders of Infinite Analytics (IA), a Boston-based company whose proprietary AI platform analyzes customers’ data. They received their EV grant to repurpose their platform for Covid containment to help governments and authorities in India with contact tracing and mobility analyses. They have since helped millions of users, and their Containment Zone analyses are becoming the bedrock for lockdown exit strategy in Mumbai and Pune. Here is a video about the project.

Mohammed Suhail Chinya Salimpasha

Suhail is a 19-year-old senior grade homeschooler. He dropped out of high school to work on finding new ways to quantify protein in serum applied on a faster diagnosis of malnutrition. This is his TedX talk on the project.  He diverted his efforts towards Covid, to create India’s first multi-language Covid symptom checker, which was adopted by some local authorities before the Government mandated an alternative.  He is currently working on solving problems in containerizing applications, Enterprise Cloud, low latency API communication, and 5G In Social Tech Democratization.

Manasseh John Wesley

Manasseh John Wesley is a 21-year-old from Hyderabad, India, studying engineering and technologies like embedded systems megatronics/machine learning/data science/digital communication systems. He is the founder of River Bend Data Solution, a data science company with health care applications. He received an EV grant to create a platform for hospitals to provide X-rays and CT scan images and to use AIML to identify at risk districts in Andhra Pradesh.

Vidya Mahambare and Sowmya Dhanaraj

Dr. Vidya Mahambare is a Professor of Economics at Great Lakes Institute of Management working in macroeconomics as well as cultural and social economics issues. Dr. Soumya Dhanaraj is an assistant professor of economics at the Madras School of Economics, working in Development Economics and Applied Microeconomics. Their grant is to support their work in labor market and migration distortions.

Onkar Singh

Onkar Singh Batra is a fourteen-year-old web developer from Jammu and Kashmir. He developed and published his first website at the age of seven and holds the record for the World’s Youngest Webmaster. Furthermore, his book ‘When the Time Stops’ made him hold the record for the record of ‘World’s Youngest Theoretical Author.’ Recently, responding to the Covid pandemic, he received his EV grant for the web applications named –‘COVID Care Jammu’ and ‘COVID Global Care’, which connects doctors with users and helps users do a free anonymous Covid Risk Assessment test.  Onkar built his website keeping in mind slow internet speed and limited access. He has plans for many future projects, including working on a bio shield for 5G radiation technology.

Nilay Kulkarni

Nilay Kulkarni is a 20-year old software developer and he previously worked on a project to prevent human stampedes at the world’s largest gathering – the Kumbh Mela. His project’s implementation at the 2015 edition of the event in Nashik, with over 30 million attendees, led to the first stampede-free Kumbh Mela in the city’s history. Nilay has also spoken at TEDx New York about the project. He has worked on assistive technology for people with ALS enabling them to control phones using their tongues. He received his EV grant for the tech development of the MahaKavach App, the official quarantine monitoring and contact tracing platform adopted by the state government of Maharashtra. So far, the platform has helped reduce the time needed for contact-tracing from 3-4 days to 25-30 minutes, and he is now working on open-sourcing the platform for greater impact.

Data Development Lab

Drs. Paul Novosad and Sam Asher are previous EV grantees for creating the SHRUG database at Data Development Lab. The SHRUG is an ultra-clean geocoded database describing hundreds of dimensions of socioeconomic status across 8,000 towns and 500,000 villages in India. Everything in the SHRUG is carefully linked, extensively vetted and documented, and ready for immediate application. In addition to continually expanding the SHRUG, they recently received another EV grant for a second platform oriented toward informing the COVID-19 response in India. This platform has a wealth of linked pandemic-related data (e.g. hospital capacity, health system use, agricultural prices) not available anywhere else and is directly feeding several COVID response research and policy teams.

Deepak VS

Deepak VS is a 23-year-old Mechatronics Engineer from Bangalore, India and he has worked on traffic and communications projects. He also founded a college club called 42 Labs that eventually grew into a startup company called Tilt, a shared mobility platform designed for Indian campuses but now in corporate parks, colleges, townships, and cities across India. Working primarily with electric bikes, Tilt is partnering with companies to help provide alternate mobility solutions to people who typically use crowded and unsafe public transport.

Amit Varma and Vivek Kaul

Amit Varma is one of the most influential podcasters in India, and the winner of the Bastiat Prize in Journalism for his writing. He is the host of the iconic longform interview podcast The Seen and the Unseen, my chat with him on Stubborn Attachments is here and Alex’s appearances on the show here and here. Vivek Kaul is a prominent journalist and writer covering finance and economics. His most recent book, “Bad Money: Inside the NPA Mess and How It Threatens the Indian Banking System” was released earlier this month.

Amit and Vivek received their Emergent Ventures grant for their new podcast “Econ Central.” You can find Econ Central episodes here.

Raman Bahl

Raman Bahl is a 2012 Teach For India Fellow. He has worked over the last decade in different capacities to teach students, train teachers, create curricula, and create systems of teaching and learning in the Indian education system. In the light of the pandemic, rural communities in India are not getting access to quality learning at home. In particular, students from poorer and marginalized groups cannot access to remote/online education launched by local schools because they lack internet access, televisions, and/or learning materials. Raman received his EV grant for creating a Voice-based Academic System for students in rural communities, to enable access to learning at home, through mobile phones. He is launching the system in Purkhas Rathi in Haryana and hopes to scale the system to more villages and states.

PickMyWork

Vidyarthi Baddireddy, Utsav Bhattacharya and Kajal Malik are Indian entrepreneurs focused on the employability of graduating students in India. In 2017 they founded Reculta to digitize campus placements. In 2019, they launched PickMyWork, a platform for onboarding gig workers and getting them to complete tasks for client organizations through a pay-per-task model. In light of the manpower crisis during the Covid pandemic, especially on the frontlines, they want to enable matching of volunteers to emergency situations. They received their EV grant for adapting PickMyWork as a local volunteer response system to emergency situations like Covid by using the platform to source, train and deploy volunteers across various projects and locations.

Harsh Patel and Hiten Patel

Harsh Patel is an undergraduate student in electronics and communication engineering; his interests are in components, coding, and robotics. Hiten Patel is an electrical engineer interested in robotics, coding, and designing. They received their EV grant to develop robot prototypes that they call ‘E-Bot: Arogya Sahayak’ to potentially support hospitals, hotels, airports, workplaces, etc., to assist with basic tasks while maintaining social distancing.

Vinay Débrou

Vinay Débrou studied computer science and is a self-taught data scientist interested in psychology, data science, and new applications of network science for collaboration-generating contexts. He has also built resources for aspiring location-independent free-agents including a curated resources library and a weekly newsletter. Vinay received his Emergent Ventures grant to accelerate his ongoing project to build a network visualization/mapping tool (v0.1 here) to catalyze cross-disciplinary expertise-sharing and collaboration in Yak Collective – an open, networked community of 300+ (and growing) independent creators, consultants, and researchers.

Those unfamiliar with Emergent Ventures can learn more here and here. EV India announcement here. To apply for EV India, use the EV application click the “Apply Now” button and select India from the “My Project Will Affect” drop-down menu.

If you are interested in supporting the India tranche of Emergent Ventures, please write to me or to Shruti at [email protected] I believe we are seeing a blossoming of talent from India comparable to that from Central Europe in the early part of the 20th century.

My Conversation with Nathan Nunn

Here is the transcript, audio, and video.  Here is part of the summary:

Nathan joined Tyler for a conversation about which African countries a theory of persistence would lead him to bet on, why so many Africans live in harder to settle areas, his predictions for the effects of Chinese development on East Africa, why genetic distance is a strong predictor of bilateral income differences and trade, the pleasant surprises of visiting the Democratic Republic of Congo, the role of the Catholic Church in the development of the West, why Canadian football is underrated, the unique commutes of Ottawans, the lack of Canadian brands, what’s missing from most economic graduate programs, the benefits of studying economics outside of the United States, how the plow shaped gender roles in the societies that used it, the cultural values behind South Korea’s success, and more.

Here is one excerpt:

COWEN: If you try to think, say, within Africa, what would be some places that you would be modestly more optimistic about than, say, a hedge fund manager who didn’t understand persistence? What would a few of those countries be? Again, recognizing enormous noise, variance, and so on, as with smoking and lung cancer.

NUNN: If I’m true to exactly what I was just saying, then southern Africa or places where you have a larger population of societies that historically were more developed. South Africa, you have the Afrikaans, and they have a different descent than others. That’s if I’m true to what I was saying. But that’s ignoring that, also within Africa, you had a very large number of successful, well-developed states, and that was prior to European colonialism and the slave trade. So one could look at those cases.

One area that I worked at, the Democratic Republic of Congo, where you had the great Congo Kingdom, the Kuba Kingdom, a large number of other kingdoms, the Luba for example — that would probably be one country. That country today is pretty much as low as — in terms of per capita income — as you can be, right at subsistence. But if we’re predicting just based purely on persistence and historical state formation, that would be one to pick.

COWEN: What do you find to be the most convincing account of Botswana’s relative economic success?

NUNN: A few things. One is, Botswana is pretty small in terms of population. Anytime you have smaller countries, you can have more extreme outcomes. That’s one, that it’s small. But then related to that, it’s, in general, ethnically homogenous, particularly compared to other countries within Africa. The Tswana are the predominant ethnicity. They also have a historical social structure, and I think that was pretty well maintained and left intact. That’s a big part of the explanation.

And:

COWEN: Is it fun to visit Democratic Republic of Congo?

NUNN: Yeah, it’s great. Yeah.

COWEN: Tell us what’s fun. I need to go once I can.

NUNN: Yeah, it’s really, really great. The first time we went as a team — this is James Robinson, Sara Lowes, Jonathan Weigel in 2013 — we were pretty apprehensive. You hear a lot of stories about the DRC. It sounds like a very unsafe place, et cetera. But one thing we didn’t realize or weren’t expecting was just how lovely and wonderful the people are.

And it turns out it’s not unsafe in general. It depends on different locations. In the east, definitely near Goma, it’s obviously much, much less safe. But I think what, for me, is wonderful is the sense of community. Because the places we go are places that haven’t been touched, to a large extent, by foreign aid or NGOs or tourism, I think we are treated just like any other individual within the community.

And:

COWEN: What’s your favorite movie and why?

NUNN: Oh, favorite movie. [laughs] That’s a good question. Favorite movie — in the past it was Dazed and Confused. I must have watched that in university about a hundred times.

COWEN: A wonderful film.

Recommended, interesting throughout.

Will private K-12 schools be reopening?

“As of July 22, pretty much across the board, [private] schools are planning for some sort of in-person learning in the fall,” said Amy McNamer, executive director of the Association of Independent Schools of Greater Washington, which supports 76 private schools in the region. “And I have to add this big caveat that that could change,” she said.

In online forums, parents are asking one another for advice about private schools, saying they fear that virtual learning at their public schools will be a disaster.

Here is much more from The Washington Post.  Of course you will note that private decisions doth not a social optimum make.  Nonetheless these particular private decisions do internalize the risks to children, parents (grandparents?), and teachers, albeit not the case load of broader society.

And those institutions are planning on reopening.  We’ll see if they get there.

The economics of fungi

One part of the mycelium had access to a big patch of phosphorus.  Another part had access to a small patch.  She was interested in how this would affect the fungus’s trading decisions in different parts of the same network.  Some recognizable patterns emerged.  In parts of a mycelial network where phosphorus was scarce, the plant paid a higher “price,” supplying more carbon to the fungus for every unit of phosphorus it received.  Where phosphorus was more readily available, the fungus received a less favorable “exchange rate.”  The “price” of phosphorus seemed to be governed by the familiar dynamics of supply and demand.

Most surprising was the way that the fungus coordinated its trading behavior across the network.  Kiers identified a strategy of “buy low, sell high.”  The fungus actively transported phosphorus — using its dynamic microtubule “motors” — from areas of abundance, where it fetched a low price when exchanged with a plant root, to areas of scarcity, where it was in higher demand and fetched a higher price.  By doing so, the fungus was able to transfer a greater proportion of its phosphorus to the plant at the more favorable exchange rate, thus receiving larger quantities of carbon in return.

We still do not understand how those behaviors are controlled.  And that is all from the new and excellent Merlin Sheldrake book Entangled Life: How Fungi Make Our Worlds, Change Our Minds, & Shape Our Futures.

Ho hum, nothing to see here, move along…

Numerous associates of the Pentagon program, with high security clearances and decades of involvement with official U.F.O. investigations, told us they were convinced such crashes have occurred, based on their access to classified information. But the retrieved materials themselves, and any data about them, are completely off-limits to anyone without clearances and a need to know.

We were provided a series of unclassified slides showing that the program took this seriously enough to include it in numerous briefings. One slide says one of the program’s tasks was to “arrange for access to data/reports/materials from crash retrievals of A.A.V.’s,” or advanced aerospace vehicles.

Our sources told us that “A.A.V.” does not refer to vehicles made in any country — not Russian or Chinese — but is used to mean technology in the realm of the truly unexplained. They also assure us that their briefings are based on facts, not belief.

That is from Ralph Blumenthal and Leslie Kean at the New York Times.  And yes there is a hat tip, and a deeply deserved one too.

A modest case for school reopening at the margin

That is the topic of my latest Bloomberg column.  Here is one excerpt:

First and most important, there is a distinction between children spreading the virus and children spreading the virus through school activities. The case against a physical reopening rests on the public health dangers, but the relevant question is relative.

Even if the schools do not physically reopen, children will still hang out together. This is especially true for teenagers, and they are also a group that, in a South Korean study, can readily spread the virus to others. Not many parents are going to quarantine their 15-year-olds at home for many months, much less their 17-year-olds. Recall that Romeo and Juliet were teenagers and came together as lovers against extreme parental opposition and during a time of plague.

It is possible that these children will spread the virus less if they were at school than if they were spending time together on their own. At least at school there would be teachers and other staff to enforce some measure of social distancing and proper hygiene practices, such as regular hand-washing…

To be sure, it’s by no means certain that schools will be safer places for children; whether they are will depend on the region. Still, the mere citation of public health dangers isn’t quite as decisive an argument against physical reopening as it may seem.

I believe I was first prompted to consider this argument by some tweets by Amihai Glazer.

Tuesday assorted links

1. “My thought is that the fact that we consume contemporary media in isolation has made made people more receptive to demonization, with its totalitarian characteristics. This is probably accentuated by the virus-induced isolation, which increases our use of contemporary media and reduces our social interactions.”  More here from Arnold Kling.

2. Did Southeast Asian fish sauce come from ancient Rome?

3. Indian Matchmaking.  Note that foreign exoticization, and thus partial concealment of anti-PC attitudes and pproaches, is one response to “things being cancelled.”  For instance: “Let’s remove this thing from the status games being fought by white people, and maybe they won’t care very much.”  And they don’t.

4. This Kevin Lewis link about whether hedonism leads to happiness was first sent to my spam blocker.

5. DNC Platform Committee decisively defeats Medicare for All as a proposal.  POTMR.

6. Why has the Spanish response to coronavirus been so poor?

7. “Divergence dates between #SARSCoV2 and the bat #sarbecovirus reservoir were estimated as 1948 (95% HPD: 1879–1999), 1969 (1930–2000) and 1982 (1948–2009), indicating that the lineage giving rise to SARS-CoV-2 has been circulating unnoticed in bats for decades”  Link here.

Hey Thomas Nagel: bats argue a lot about where the best restaurants are!

Let’s not give them Twitter:

They found that the bat noises are not just random, as previously thought, reports Skibba. They were able to classify 60 percent of the calls into four categories. One of the call types indicates the bats are arguing about food. Another indicates a dispute about their positions within the sleeping cluster. A third call is reserved for males making unwanted mating advances and the fourth happens when a bat argues with another bat sitting too close. In fact, the bats make slightly different versions of the calls when speaking to different individuals within the group, similar to a human using a different tone of voice when talking to different people. Skibba points out that besides humans, only dolphins and a handful of other species are known to address individuals rather than making broad communication sounds.

Here is further information, here is the original research, via the excellent Samir Varma.

Ocean Grove, New Jersey travel notes

Having not visited the New Jersey shore since I was a kid (and then a very regular visitor), I realized you cannot actually swim there with any great facility.  Nor is there much to do, nor should one look forward to the food.

Nonetheless Ocean Grove is one of America’s finest collections of Victorian homes, and the town style is remarkably consistent and intact.  Most of all, it is an “only in America” kind of place:

Ocean Grove was founded in 1869 as an outgrowth of the camp meeting movement in the United States, when a group of Methodist clergymen, led by William B. Osborn and Ellwood H. Stokes, formed the Ocean Grove Camp Meeting Association to develop and operate a summer camp meeting site on the New Jersey seashore. By the early 20th century, the popular Christian meeting ground became known as the “Queen of Religious Resorts.” The community’s land is still owned by the camp meeting association and leased to individual homeowners and businesses. Ocean Grove remains the longest-active camp meeting site in the United States.

The pipe organ in the 19th century Auditorium is still one of the world’s twenty largest.

Ocean Grove, New Jersey - Wikipedia

The Auditorium is closed at the moment, but they still sing gospel music on the boardwalk several times a night.

The police department building is merged together with a Methodist church, separate entrances but both under the same roof.

Ocean Grove remains a fully dry city, for the purpose of “keeping the riff-raff out,” as one waitress explained to me.  To walk up the Ocean Grove boardwalk into nearby Asbury Park (Cuban and Puerto Rican and Haitian in addition to American black) remains a lesson in the economics of sudden segregation, deliberate and otherwise.

Based on my experience as a kid, I recall quite distinct “personae” for the adjacent beach towns of Asbury Park, Ocean Grove, Bradley Beach, Seaside Heights, Lavalette, Belmar, Spring Lake, and Point Pleasant.  This time around I did not see much cultural convergence.  That said, Ocean Grove now seems less the province of the elderly and more of a quiet upscale haunt, including for gay couples.  As an eight-year-old, it was my least favorite beach town on the strip.  Fifty years later, it is now striking to me how much the United States is refusing to be all smoothed over and homogenized.

Monday assorted links

1. Fryer responds, in my opinion we are back to where we started after initial publication of his piece.

2. German wealth inequality is extreme.

3. Japanese building a dam almost entirely with robots.

4. Emmanuel Farhi has passed away, here is an earlier interview with him.

5. It was the later Harvard economist Robert Dorfman who came up with the pooled testing idea in 1943 to solve WWII problems.  To test recruits for syphilis, of course.

Does Joining the S&P 500 Index Hurt Firms?

It seems to these days:

We investigate the impact on firms of joining the S&P 500 index from 1997 to 2017. We find that the positive announcement effect on the stock price of index inclusion has disappeared and the long-run impact of index inclusion has become negative. Inclusion worsens stock price informativeness and some aspects of governance. Compensation, investment, and financial policies change with index inclusion. For instance, payout policies of firms joining the index become more similar to the policies of their index peers. ROA falls following inclusion. There is no evidence of an impact of inclusion on competition.

That is from Benjamin Bennett, René M. Stulz, and Zexi Wang.  Here is the NBER paper, here is an ungated copy.

Experienced Segregation

Here is a new and important paper from Susan Athey, Billy A. Ferguson, Matthew Gentzkow, and Tobias Schmidt:

We introduce a novel measure of segregation, experienced isolation, that captures individuals’ exposure to diverse others in the places they visit over the course of their days. Using Global Positioning System (GPS) data collected from smartphones, we measure experienced isolation by race. We find that the isolation individuals experience is substantially lower than standard residential isolation measures would suggest, but that experienced and residential isolation are highly correlated across cities. Experienced isolation is lower relative to residential isolation in denser, wealthier, more educated cities with high levels of public transit use, and is also negatively correlated with income mobility.

Here is the NBER link.  Here is an earlier and ungated version.

What are fungi?

I don’t view this as a formal answer, but it is interesting nonetheless:

Mycelium is how fungi feed.  Some organisms — such as plants that photosynthesize — make their own food.  Some organisms — like most animals — find food in the world and put it inside their bodies, where it is digested and absorbed.  Fungi have a different strategy.  They digest the world where it is and then absorb it into their bodies…

The difference between animals and fungi is simple: Animals put food in their bodies, whereas fungi put their bodies in the food.

…to embed oneself is an irregular and unpredictable food supply as mycelium does, one must be able to shape-shift.  Mycelium is an living, growing, opportunistic investigation — speculation in bodily form.

That is from the new and excellent book by Merlin Sheldrake, Entangled Life: How Fungi Make Our Worlds, Change Our Minds, & Shape Our Futures.