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Thread: POTF 44 - Winner and Runner Up

  1. #1

    Default POTF 44 - Winner and Runner Up

    The winner of POTF 44 was Lord Thesaurian, earning 1 competition point and 5 rep points. Well done!

    Winning Post

    Quote Originally Posted by PoVG
    Countries that followed strict lock down procedures properly like New Zealand certainly benefited the most. Those that did a half-assed job merely mitigated the outcome while also lengthening the process. On the other hand, those that had less lock down procedures enacted ended up creating a lock down environment as well as the extra deaths.
    This assertion has been reduced to an unfalsifiable appeal to purity built on an anecdote. It’s worth repeating that the pandemic was declared before NZ went into lockdown, and at that stage, WHO recommendations indicate mass quarantines will no longer be effective and should therefore not be used as the costs of implementation likely exceed potential benefits. Parsing demographic and geographic factors from the lockdown impact in a single country will require the full perspective of hindsight, but the odds of a potential counter factual being significant enough to countervail the trend we’re seeing in the current as well as previous pandemics regarding the (in)efficacy of lockdowns are inherently low.

    This would make NZ an outlier, best case, given its geography and low population density isolated it from international spread since the beginning of the outbreak by default. It would have been in a completely different place relative to more interconnected regions that were sitting on hundreds or thousands of undetected cases by the time major NPIs were adopted.

    It’s also untrue overall that less restrictive interventions led to increased case growth relative to more restrictive measures. As cited earlier:
    Implementing any NPIs was associated with significant reductions in case growth in 9 out of 10 study countries, including South Korea and Sweden that implemented only lrNPIs (Spain had a nonsignificant effect). After subtracting the epidemic and lrNPI effects, we find no clear, significant beneficial effect of mrNPIs on case growth in any country. In France, for example, the effect of mrNPIs was +7% (95% CI: -5%-19%) when compared with Sweden and + 13% (-12%-38%) when compared with South Korea (positive means pro-contagion). The 95% confidence intervals excluded 30% declines in all 16 comparisons and 15% declines in 11/16 comparisons.

    Conclusions: While small benefits cannot be excluded, we do not find significant benefits on case growth of more restrictive NPIs. Similar reductions in case growth may be achievable with less-restrictive interventions.
    Quote Originally Posted by PoVG
    The studies that look at lock down measures, however, always try to simplify it which is a really bad way to look at it. There are many factors in play:
    How widespread lock down measures were applied?
    How strict were each lock down measure applied?
    How well did the public follow them?
    How well was it enforced?
    How much does the public try to circumvent the measures?

    Simply saying restaurants are closed while people are getting together in their houses more doesn't really tell us the full picture if the latter is not accounted for. This is pretty much what most, if not all, studies, even those that show positive effects for lock downs, fail to satisfy. They're too simplistic.
    The “ more restrictive vs less restrictive” study looked at ~50 different NPIs from 11 major countries including Sweden, South Korea, the UK and Germany. Omitted variable bias is a major reason why the efficacy of lockdowns observed in some studies is statistically overstated.

    A good example of that is the Flaxman paper referenced earlier and probably in every lockdown discussion since its publication. Professionally or otherwise, it’s been cited hundreds of times as evidence lockdowns work.
    Our results show that major non-pharmaceutical interventions—and lockdowns in particular—have had a large effect on reducing transmission. Continued intervention should be considered to keep transmission of SARS-CoV-2 under control.
    The way the result was determined suggests the conclusion relies on a causation fallacy, which could be why it doesn’t hold when comparing more vs less restrictive NPIs across countries. The reason for this, in the context of the Flaxman study, is their model retroactively uses the number of deaths to predict future deaths under NPIs vs no NPIs and determined that NPIs reduce transmission.

    That’s a fairly obvious conclusion, but to stretch this into a claim that “lockdowns in particular” caused it is mostly conjecture. As I said earlier, it’s unsurprising a study, looking at countries in the same region and adopting the broadly similar strategies, found lockdowns were correlated with reduced transmission. What’s odd is that Flaxman et al, determining the efficacy of lockdowns vs a few other categories of NPIs, don’t appear to address the fact that their own model predicts Sweden’s NPIs reduce Rt as much as other lockdown countries, including significant overlap with Denmark and Norway.
    Spoiler Alert, click show to read: 

    Also significant, I think, is that the predicted range of NPI impact is arguably more precise for Sweden than other countries in the model, and yet not much less than the most generous predictions for lockdowns’ impact on Rt. Flaxman and colleagues determine 3-3.5 million lives were saved by NPIs, but don’t mention the caveat in their conclusion this is due to “lockdowns in particular.” The model does not necessarily show this, even under its a priori assumption that all NPIs have the same multiplicative effect on Rt. The latter assumption is significant given it means the effect of any NPI on the model predictions will be equally strong in the first place, and even then, lockdowns don’t appear to have been especially impactful relative to other NPIs.

    The reason the authors deduced a particularly strong effect of lockdowns is because most countries in the sample, all except Sweden, employed lockdowns in similar time periods, producing an outsized effect on the model by virtue of being a common factor relative to other kinds of interventions. Because the model attributes 100% of the reduction in Rt to government interventions at the outset, the commonality of lockdowns is predisposed to have a dominant effect, which seems to have led the authors to a correlation/causation fallacy. The results of the model actually suggest less restrictive NPIs did most of the heavy lifting across all countries in the sample, relative to lockdowns. This matches the conclusions of the comparison between mrNPIs and lrNPIs

    The flaw in Flaxman’s argument is observed in other research, due in part to the difficulty of accurately weighting the probable effects of individual variables in a Bayesian model.

    The peculiar aspect of the claim that lockdown accounts for 81% of the reduction in R 0, is that Sweden did not implement any lockdown, but still see a similar decrease in R 0 as the other countries, even though the other NPIs were reported to have no substantial effect on R 0. To solve this problem, as compared with the authors’ earlier work9, which showed a significantly higher R 0 for Sweden, they invoke a country-specific last intervention parameter, which is only implemented for Sweden10 (see equation i). The “last intervention” parameter is multiplied with R 0, and can therefore be seen as a parameter adjusting the model for Sweden independently. As can be seen, when analysing the posterior distributions of the intervention parameters, the “last intervention” parameter for Sweden results in 73.5 % of Sweden’s reduction in R 0 (Figure 1). The last intervention impact on R 0 is not reported or discussed in the Nature publication, possibly misleading decision-makers on the importance of lockdowns.

    In conclusion, it is peculiar that the model displays an almost identical change in R 0 in all countries, dropping sharply below one at the final NPI, independently on the nature of that NPI. In reality, all countries had different NPIs implemented at different time points, likely with varying strength and efficiency, and it is quite likely that NPIs such as enforcing social distancing at least had some effects, not seen in the models. Given the importance the initial report had on government policies and the fact that we show here that the conclusions made about the significance of the lockdown are not entirely correct, we do think that we should pinpoint this to readers and policymakers. Correct assumptions on the effects of NPIs are becoming even more urgent as many nations still are imposing different NPIs, and that these might go on for an extended period
    Because modeling attributes virtually all reduction in Rt to whatever NPI is used last, this indicates not only the existence of confounders but also that the common use of lockdowns is predetermined to have an oversized effect on any estimates.
    Our finding in Fact 1 that early declines in the transmission rate of COVID-19 were nearly universal worldwide suggest that the role of region-specific NPI’s imple- mented in this early phase of the pandemic is likely overstated. This finding instead suggests that some other factor(s) common across regions drove the early and rapid transmission rate declines. While all three factors mentioned in the introduction, voluntary social distancing, the network structure of human interactions, and the nature of the disease itself, are natural contenders, disentangling their relative roles is dicult.

    Our findings in Fact 2 and Fact 3 further raise doubt about the importance in NPI’s (lockdown policies in particular) in accounting for the evolution of COVID-19 transmission rates over time and across locations. Many of the regions in our sample that instated lockdown policies early on in their local epidemic, removed them later on in our estimation period, or have have not relied on mandated NPI’s much at all. Yet, e↵ective reproduction numbers in all regions have continued to remain low relative to initial levels indicating that the removal of lockdown policies has had little e↵ect on transmission rates.

    The existing literature has concluded that NPI policy and social distancing have been essential to reducing the spread of COVID-19 and the number of deaths due to this deadly pandemic. The stylized facts established in this paper challenge this conclusion. We argue that research going forward should account for these facts when assessing how important NPI policy is in shaping the progression of COVID-19.
    Quote Originally Posted by PoVG
    Taiwan is a good case of early strong response that made it possible that they don't even need to consider a full lock down.
    Taiwan certainly did respond earlier than most other countries, thanks in part to its network of contacts on the mainland that passed information on the outbreak during the time Beijing was still trying to cover it up. Subsequent miscommunication from the WHO, probably in deference to China, about human transmission also delayed appropriate response by other countries, to the extent Taiwan’s NPIs came a month earlier than most. It would be a misnomer to say acting “early enough” makes lockdowns unnecessary, because lockdowns are ineffective beyond the earliest phases of an outbreak in the first place, which had likely passed by the time China publicly acknowledged the outbreak in Wuhan and announced countermeasures. This fits the findings from earlier research, which found the spread of Covid could have been confined to a regional outbreak had Chinese authorities put in place NPIs that were delayed 3-4 weeks by the coverup effort.

    Runner-ups this week are Iskar and sumskilz. See you next time!

    Runner Up Post

    I've been going through my somewhat rusty understanding of relativity again given the occasion and started to draw Minkowski diagrams to get my thoughts in order. Since I think they are actually quite helpful in understanding what "time travel" in the context of relativity actually means, I jotted them down digitally and added a bit of an introduction for those unfamiliar with them:

    Minkowski diagrams are a standard way of depicting what happens in special relativity. "Special" meaning we're not dealing with the crazy of curved space yet, just the speed of light as a finite upper limit (including for the transmission of information).
    This is a basic Minkowski diagram, as of yet unpopulated:
    Spoiler Alert, click show to read: 

    In order to make things representable we restrict ourselves to one space dimension, so what you see before you is not a spatial plane, but a one dimensional space (a line) and a time axis forming a flat 2D spacetime. Usually one chooses the units on the two axes such that the speed of light corresponds to one space unit per time unit, i.e. light emitted from the origin of this diagram moves on the yellow dotted lines towards the future.
    Since the yellow dotted lines represent the speed of light (remember, this is a space-by-time diagram), they form two cones with respect to the origin. The upper one is called the future cone, containing all events (points in spacetime) that you could causally influence from the origin. The lower one is called the past cone, containing all events that could causally influence the observer sitting in the origin.
    The past and future cones together only make up half of the diagram. Why? The rest is called the elsewhere (incidentally also the place where Khajiit live), and consists of those space-time coordinates that you can never reach and that can not influence you currently: You might be able to reach the space-coordinate at some time, but not at the time corresponding to these specific points in spacetime.

    Now, we populate this flat 1Dx1D world. Here is an unmoving observer sitting in the origin:
    Spoiler Alert, click show to read: 

    The arrow does not indicate movement in space in this case (the space coordinate does not change), but simply the passage of time. These curves showing which point in space is passed by an observer at which point in time are called worldlines.
    If you start moving around, they will look like this:
    Spoiler Alert, click show to read: 

    The observer in our example is moving at half the speed of light, they are making one unit of space in two units of time. This example also allows us to demonstrate the concept of time dilation: Say you left a clock sitting at rest at the origin and then take off at half the speed of light. After you have travelled one space unit (taking two units of your Eigenzeit) you take a look back at the clock sitting in the origin. Naively (or newtonially) one would depict "looking back at the origin" by the black dotted line. However, since "looking" means you have to receive light rays reflected of the clock in your eyes, we may not draw a horizontal line from you to the vertical line representing the origin in the passage of time, we have to draw a 45 angled light ray back to the origin. Now this light ray meets the origin at the event (0 space units, 1 time unit), which means the time you are seeing on that clock in the origin is 1, not 2 as on your own watch. That means that from your perspective time at the origin is advancing more slowly than with you.
    This is the first effect on the passage of time one has to consider: Since measurement of time at different spacetime points involves the transmission of information, which happens at most at the speed of light, movement changes what time coordinates we measure for distant points in space.

    Now a common talking point is that going faster than light means going back in time. Let us make that precise, as it will turn out that what you get from superluminal speeds is pretty far from a naive "turning up in your own past" DeLorean-style. Here is the worldline of a hypothetical observer that somehow managed to go at double the speed of light:
    Spoiler Alert, click show to read: 

    If we apply the same principle as above for reading off the time at the origin (we left a clock there again), we see that the time at the origin seems to be -1, so indeed it seems like we travelled back in time with respect to the origin. However, your Eigenzeit ("own-time") still progressed by one unit to 1. Furthermore, since we left the origin, we cannot influence its past in any way anyhow (our own future light cone still only contains future points of the origin). The only thing we have achieved so far is that while looking back at the origing it looks like time at the origin is going backwards (i.e. we receive earlier and earlier light signals emitted by the resting clock).

    Frustrated by this ineffective method of "time travel" we decide to turn around and travel back to the origin at double the speed of light, which looks like this:
    Spoiler Alert, click show to read: 

    Now something funny happens: Suppose we left a farewell/welcoming party committee at the origin and they are looking at us to see when we turn around, so they can prepare the party. They are in for a surprise: We arrive back at the origin way before they even see us turning around. Why? The event of us turning around (a) emits a ray of light travelling towards the origin at the speed of light. But since we travel at double that speed the events of us passing Alpha Centauri (b) and the Kuyper Belt (c) emit rays of light that arrive even earlier at the origin. In toto, seen from the origin our journey back seems to be entirely backwards: First we arrive completely unforeseen (literally) at time 2, then they see us moving backwards via c, b, a to the point of turning around on our superluminal voyage - all the while we're standing next to them on earth! The only "causal" stunt you could pull here is shooting a laser cannon at one of your friends from (a), then travel back to earth, and comfortably wait until it arrives one time unit later to either heroically save your friend or murder them with the perfect alibi - but that's just (slightly psychopathic) cosmic one-man-runaround ping pong, not actual time travel.

    So, superluminal speeds make the succession of time measured between observers moving relative to each other somewhat awkward, but doesn't really create time travel opportunities.

    There is one interesting effect of superluminal speed though: It changes what events are contained in your past and future cones in a weird way. Here's ordinary, sublight travel:
    Spoiler Alert, click show to read: 

    You move at half the speed of light from the origin along the arrow representing your worldline. When you arrive, the green dotted lines represent your new future and past cones. Notice that the new future cones is always contained in any older future cone (e.g. the yellow one from sitting in the origin earlier), and that the new past cone containes all older past cones. In other words, the passage of time narrows down what you can potentially influence in the future, while it adds new events that can potentially influence you.
    Now this only holds for sublight speeds. Here's the same diagram for travelling at twice the speed of light:
    Spoiler Alert, click show to read: 

    Notice how the green future cone is no longer contained in the yellow one, and the green past cone no longer contains the entirety of its yellow counterpart. In particular the blue area used to be part of your past, but is no longer, while the orange area used to be in your "elsewhere" and has now become part of your future. Caution, though: "Past" and "Future" do not mean sections of your worldline here, but the cones of events that can potentially influence you/that you can potentially influence.

    So far for special relativity in a flat spacetime. Of course things are more complicated in general relativity (of which special relativity is a linear approximation for small areas of low energy/mass if you will), and spacetime itself being curved could, at least, theoretically create settings where you can actually have loops in your worldline (vulgo: arrive in your own, actual, past, and say hello to yourself like Spock). This can only happen, though, if spacetime is topologically non-trivial, i.e. if it "has holes" like a donut:
    Spoiler Alert, click show to read: 

    In the example above our 2D spacetime is curved and sports a kind of handle-like structure in addition to the mostly flat part. If you ignore the "entrance" or "exit" of the handle you can just move around ordinarily in spacetime (1), but if you "travel" through the handle (remember, one of the dimensions is time!) you could end up with a loop in your worldline (2). However, this kind of topological structure is highly unlikely and/or requires immense amounts of mass/energy to maintain. Some used to posit that black holes could create the ruptures in spacetime that are the "entrance" and "exit" in the image above (and then only need to "link up" to create such a "wormhole"), but Hawking and Penrose have shown that Quantum effects prohibit black holes from actually reaching infinite curvature at the centre, so it is unlikely spacetime actually "rips".

    In toto, this is crazy, but doesn't really provide us with means for time travelling in the more common sense. For anyone interested in further reading I can recommend Richard Gott, "Time travel in Einstein' universe".

    Runner Up Post

    Quote Originally Posted by antaeus View Post
    And when we're talking genetics, even nationalities and cultural identities are only of coincidental relevance - there being no genetic basis for culture. But then we're talking changes occurring over 1 or 2 generations, so I don't think we're seeing selective breeding here. If anything, we're seeing nutrition and standard of living allowing for potential to be realised.
    In the absence of strong evidence to the contrary, I'm inclined to agree that the measured changes are (at least primarily) environmental. That said, what you've written here are to some degree widely held misconceptions. The reality is more complicated.

    The predominate genetic predispositions of a population will influence its culture. Likewise culture itself is a significant selection pressure. One example, is the fact that pastoralist cultures created selection pressure for adult lactase persistence. A higher percentage of adult lactase persistence within their constituent populations subsequently created greater cultural dependence on dairy products, which in turn increased the degree of positive selection for adult lactase persistence.

    Depending on h and S in the breeder’s equation, culturally influenced changes to population genetics can potentially occur quite rapidly. An example is currently taking place in Israel where religiosity is correlated with having about 3 times as many children. Adult religiosity is ~44% heritable. Therefore, we can safely assume that there is a currently a ~39% per generation increase in the population’s relative genetic predisposition toward religiosity, because R = (.44 x .44)(3 – 1). Which in turn, will increasingly influence the country's culture. Of course, the genetic propensity for religiosity can only be a vague inclination toward certain types of thought and behaviors. The specifics are filled in by culture, of which religion is an aspect, from an anthropological perspective. In this case, most relevant is the mitzvah "be fruitful and multiply".

    Third point, due to assortative mating, nationalities and cultural identities aren’t simply of coincidental relevance for population genetics. To varying degrees, culturally derived identities determine who people are more or less likely to have offspring with. In some cases, where there is traditionally mandated endogamy for example, this can be significant. In other cases, where borders shift and there is little cultural resistance to intermarriage, the result is usually more like a genetic continuum that roughly correlates with geography. For example, there is a lot of genetic overlap between French and Germans (who are already very similar populations), to the extent that people with roots close to the borders may have more ancestry in common with people immediately across the border than those at the far end of their own nation.

    Last edited by Septentrionalis; May 31, 2021 at 12:31 PM.

  2. #2

    Default Re: POTF 44 - Winner and Runner Up

    Apologies for the inconvenience. I am doing this for the first time and I am unable to get the full original posts by our contestants (with their quotations intact) into the announcement, so I only included the URLs for now.

  3. #3

    Default Re: POTF 44 - Winner and Runner Up

    Quote Originally Posted by Enros View Post
    You don't seem to be familiar with how the burden of proof works in when discussing social justice. It's not like science where it lies on the one making the claim. If someone claims to be oppressed, they don't have to prove it.

  4. #4

    Default Re: POTF 44 - Winner and Runner Up

    Now a bit better, sumskilz!


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