• Epidemiology’s Time of Need : COVID-19 Calls for Epidemic-Related Economics - American Economic Association
    https://www.aeaweb.org/articles?id=10.1257/jep.34.4.105

    The COVID-19 pandemic has catapulted scientific conversations and scientific divisions into the public consciousness. Epidemiology and economics have long operated in distinct silos, but the COVID-19 pandemic presents a complex and cross-disciplinary problem that impacts all facets of society. Many economists have recognized this and want to engage in efforts to mitigate and control the pandemic, but others seem more interested in attacking epidemiology than attacking the virus. As an epidemiologist, I call upon economists to join with us in combating COVID-19 and in preventing future pandemics. In this essay, I attempt to provide some insight for economists into how epidemiology works, where it doesn’t work, and the much-needed answers that economists can help us obtain. I hope this will spur economists towards an epidemic-related economics that can provide a blueprint for a healthy economy and population.

    The principles of epidemic dynamics, prevention, and elimination are well-established and have been tested in disease outbreaks, large and small, as well as in computational models and laboratory experiments. There is no more reason for economists to jump into the production of epidemiology models than there is for them to become atmospheric scientists

    À noter un intéressant passage sur la distinction entre « applied epidemiology » et « academic epidemiology », sur la question des masques.

    sur les épidémiologistes en chambre (comme vous et moi) :

    Many early attempts by non-epidemiologists (or epidemiologists with no experience in infectious diseases) to understand or predict COVID-19 went wrong when analysts either assumed that initial data would continue to describe the changes in disease spread over time, or that initial data could only be biased in one direction

    et sur les modèles « worst case » dont on a entendu parler au début :

    When critics argue over what high-profile epidemiology models “got wrong” about the COVID-19 pandemic, their analysis presupposes that the goal of these models was to predict, with both validity and accuracy, the actual total number of cases and deaths expected throughout the course of the pandemic under actual pandemic responses at both the individual and governmental levels. It is absolutely the case that both the high-profile Imperial College (Ferguson et al. 2020) and Institute for Health Metrics and Evaluation (IHME) models (Murray 2020) as well as all other current models, fell well short of this lofty goal; this is to be expected because it was not the intended goal of these models. (...)
    But to put these concerns in real-world context, no infectious disease modeler expects to be able to accurately forecast the future based on sparse data from early in a pandemic. Even “nowcasting,” the task of modeling the current number of true infections, is extremely challenging, especially early in a pandemic. Asking an infectious disease modeler to predict the exact trajectory of an outbreak is akin to asking an economist to select stocks for your portfolio or a climate scientist to predict the best day in 2022 for an outdoor wedding.

  • So why is it that in lower-income countries, richer people emigrate more? What does that mean about the effects of immigration?

    @MariapiaMendola and I went all-out to find answers, using survey data on 653,613 people in 99 countries.

    Start with the facts. This shows 120,000+ people in low-income countries (Malawi, Laos,…). The orange bell-curve is the distribution of income (0=average). The blue line (with confidence interval) is the probability that people at each income are actively preparing to emigrate:

    This is not actual migration, but people who report that their intent to migrate has recently culminated in a very costly action, like purchasing international travel or applying for a visa.

    We show in the data that relatively richer people, as you would expect, are better able to turn their migration wishes and plans into reality than poorer people. So the line for actual migration, by income, should be even steeper than the blue line above.

    That has two remarkable implications. First, when poorer people get more money, they often invest it in… migration.

    This has been found in specific settings around the world. @SamuelBazzi rigorously showed this happening in rural Indonesia:

    https://www.aeaweb.org/articles?id=10.1257/app.20150548

    The second implication is about what happens to immigration on the other end.

    It means that the “additional” migrants caused by rising income in the origin country are likely to possess more & more of the things that make workers earn more, like education or work ethic.

    In the cold, hard economic terms used in the literature, it means that rising incomes in developing countries mean 1) higher propensity to emigrate from the origin and 2) more “positive selection” of immigrant workers at the destination.

    https://www.cgdev.org/publication/migration-developing-countries-selection-income-elasticity-and-simpsons-parad

    What’s going on here? Is it that richer people have an easier time paying to migrate? Is it that richer people invest more in things that facilitate migration, like schooling? Is it demographic change accompanying rising incomes?

    The literature posits all of these and others.

    And why is it so difficult for people, especially many smart people in the policy world, to accept these facts?

    I want to address all these with two pictures from the paper.

    First, pool all the surveyed people in 99 countries into one graph. As people begin to earn the (price-adjusted) equivalent of thousands of dollars a year, they are more & more likely to be preparing to emigrate. For the richest people, that reverses.

    Now just split exactly the same data by education level. In green, that’s people with secondary education or more. In red, people with primary education or less.

    The dashed line (right-hand vertical axis) shows the fraction of people in the green (secondary education+) group.

    That inverse-U shape, the #EmigrationLifeCycle at the household level, is greatly diminished. The emigration propensity barely rises with income within each group.

    This is informative about the origins of the life-cycle. A lot of it comes from rising investment in education, which both motivates and facilitates emigration.

    It confirms what Dao, Docquier, @ParsonsEcon, and Peri find in cross-country data:
    https://linkinghub.elsevier.com/retrieve/pii/S030438781730113X

    It also explains a lot about why the Life Cycle is so counterintuitive. For any given kind of person—like a person with a certain level of education—emigration either doesn’t rise or actually falls with higher income.

    But the process of economic development means that people are shifting between those groups. In the last picture above, you can see people moving from the low-emigration group (low education) to the high-emigration group, as incomes rise.

    If this seems like a brain twister, you’re not alone. This counterintuitive “flip” in correlations is such a common pitfall of reasoning that it has a name: #Simpson's_Paradox (https://en.wikipedia.org/wiki/Simpson%27s_paradox)

    Notice that the “groups” in Simpson’s Paradox can be any size. They can even be individual people! That is, it could both be true that 1) any given person would be less likely to emigrate if they had more income AND 2) more people emigrate if the whole country gets richer.

    There’s no contradiction there. I have sat across the table in Brussels from a brilliant development expert who said, “But people tell me personally they’re moving to earn more money. Do you think they’re lying to me?”

    They are not lying. It’s just that the relationship conditional on individual traits can be the opposite of the relationship across all individuals, because economic development brings shifts in those traits. That’s Simpson’s Paradox.

    There’s a long-read blog that goes into more depth, and links to the papers, here:
    https://www.cgdev.org/blog/emigration-rises-along-economic-development-aid-agencies-should-face-not-fear

    https://twitter.com/m_clem/status/1295735909564981249

    –—

    voir aussi le fil de discussion: “Does Development Reduce Migration ?”
    https://seenthis.net/messages/526083

    ping @rhoumour @_kg_ @karine4 @isskein

  • L’American Economic Association tient son meeting annuel à San Francisco (fini aujourd’hui) et en suivant le hashtag #ASSA2016 sur Twitter, il y a des trucs vraiment très intéressants.

    https://www.aeaweb.org/Annual_Meeting

    et
    https://twitter.com/hashtag/ASSA2016?src=hash

    The 2016 Annual Meeting will take place in San Francisco, CA
    on January 3-5, 2016 (Sunday, Monday & Tuesday). The headquarters hotel is the Hilton San Francisco Union Square; the co-headquarters hotel is the Marriott Marquis San Francisco.