Wednesday, September 1, 2021

Mismeasuring Risk In Both Directions

Sometimes it's amusing to observe just how exaggerated are people's understanding of various problems. I once quizzed someone by asking them how much the earth has warmed since pre-industrial times. They said something like, "About 15 degrees." This is from an American context, so presumably they meant 15 degrees Fahrenheit. The real answer is more like 1.8 degrees. I don't know what kind of answer you'd get if you randomly polled people, but the subject of my non-random quiz is not alone in having an exaggerated sense of how much warming there has been. A literal "climate change denier" would be closer to the truth by saying zero. I've heard similar exaggerations for the amount of sea level rise that's expected in the coming century, citing a likely rise of several meters whereas it's likely to be in the tens of centimeters. (Larger projections exist in the literature, for sure, so you could cherry pick a large value and claim the mantle of "science." I've also heard outlandish projections of how soon Greenland's ice will be gone. Again, I don't know what a proper poll would show or how close it would be to the literature's best point estimate. But the catastrophic voices are louder than the moderates.) Again, someone saying "zero" would be closer to the truth than someone who says "six meters." 

I see the same phenomenon in estimating the threat posed by covid-19. Particularly when it comes to the threat it poses to young people, some of us (and I am including myself here) have been pointing out that the risk is very small. See this chart (which actually comes from an alarmist page, and which I cited in a recent post):




One could be forgiven for rounding the IFR for the 0-34 group down to zero and commenting that the risk is something that blends imperceptibly into the background of other hazards (like auto accidents and suicide). If I'm reading this chart correctly (partially gated), when polled, people in the under 34 group estimate themselves to have a 2% (!?!) chance of death conditional on contracting covid. (Original paper here.) There's something wrong when your risk calibration is off by a factor of 500. (That's 2% over 0.004%, but I should probably apply some kind of adjustment for the consideration that 18 and younger weren't represented in the polls. Even if I did that, there's no way their assessment of risk is anywhere near what it really is.) The institutions of public health should be absolutely ashamed that they've so thoroughly misinformed the public. A young person walking around thinking s/he's not at risk, as in a true "covid denier", is actually more correct than the misinformed young people captured in these poll numbers. 

(Unfortunately, it looks like the elderly are being irrational about their risk of covid in the other direction, saying that the mortality risk is lower than it actually is. In fact they see themselves as less at risk than the young people do. That said, their self perception of risk is way closer to the ground truth than the young people's.)

There may be some attempt to defend the catastrophic worldview by saying the grossly exaggerated values are stand-ins for expected values considering tail risk. Maybe they point to the right policies and mitigation responses, even though they're wildly off in terms of quantifying the problem? In other words, a few inches of sea level rise could actually be catastrophic, so we're best off thinking that this measure is much higher than it really is. Maybe 3℃ of global warning is really terrible, even if it sounds pretty mild. Maybe it's actually as bad as 10℃ sounds to the average person. Maybe the two or three orders of magnitude difference between the perceived risk of covid and the actual risk is a stand-in for some larger truth? Like, "Of course I'm not actually at risk, but I should act as though I am, lest I transmit the virus unknowingly to someone who's vulnerable." Or, "Considering the long-term effects of covid, I'm best off treating it as if it has a much higher mortality rate than it actually does." 

I think it would be astonishing if this misperception of reality just happened to give the right answer to some other question. It would be quite a surprise if overstating the degree of global warming by a factor of seven or eight yielded the correct policy positions. It's far more likely that people who are objectively wrong about measurable quantities are also wrong about the appropriate policy fixes (and here I mean public and private policy, as in government promulgated mask mandates and personal hygiene policies). We should certainly entertain tail risk and "unknown unknowns" when it comes to global hazards like covid-19 and global warming. But we shouldn't be misstating averages or inflating known quantities. Sure, simulate a scenario where 10% of young covid victims suffer "long covid," spell out the long-term costs in dollars, lost productivity, lost year of life, etc. Then weight that scenario with some kind of plausible probability estimate, which some third party could audit and critique. Don't fudge it by exaggerating the mortality risk by a factor of 100 or more. Maybe in some cases the tail risk is so compelling that it's worth extreme mitigation measures, even though the "average" scenario is pretty ho hum. We should be able to make that argument without distorting known quantities and misleading the general public. These distortions, which are common in catastrophic rhetoric, cede the intellectual high ground to the so-called "deniers." Deniers may have a simpler, dumber model of reality, but their error is usually bounded at zero. Mistakes made by catastrophizers, by contrast, often have no ceiling. 

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Then again, maybe we're just bad about thinking about risks in the 1% range. Maybe the young people in the surveys were basically giving an answer that sounded like a small number and mentally rounding down to zero, not realizing that a 2% risk of death is a pretty big deal. I recall Maia Szalavitz reporting that young people, when asked about quantitative hazards of drug use, tended to exaggerate by some huge factor (I think this was in her book Unbroken Brain). And yet they engage in drug use at much higher rates than their elders. That seems consistent with the exaggerated risks captured in the paper above. Still, there is something very wrong going on here. The public health establishment, if it's doing its job, should be correcting such hugely distorted perceptions, not leveraging them to make people do the right things for the wrong reasons. It should be telling young people that they can venture out and comingle with other young people (while still being cautious around the elderly and vulnerable). 

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