Parsing US vaccine forecasts

This post is an experiment based on a simple idea: Readers care about the future; crowdsourced forecasts are one relatively reliable way to predict the future; so journalists should use those forecasts as grist for journalism. What might that look like?

President Biden has said all adults in the US will be eligible to get a vaccine by May 1, and that there will be enough vaccine supply for all of them by the end of May. Will the US reach that goal?

Forecasters on crowdsourced forecasting platforms have been growing more and more optimistic in their assessments of vaccine supply, and while most of their forecasts don’t map precisely to Biden’s promise, they paint an optimistic picture.

Vaccine supply

Good Judgment Corp., a forecasting firm that grew out of academic research into crowdsourced forecasting, maintains a public dashboard of Covid-related forecasts by its “superforecasters”—individuals with a track record of high accuracy forecasting geopolitics. Those forecasters have been estimating when the US will have distributed enough vaccine doses to inoculate 100 million and then 200 million people, and they’re much much more optimistic today than a month ago.

Good Judgment gives an 85% chance that the US will have distributed enough vaccine doses for 100 million people by the end of March and a 98% chance that it will have distributed enough for 200 million people by the end of June. These questions are asking about distribution of doses not jabs in arms, so the total number of people who have received doses will slightly lag these estimates.

There are about 250 million adults in the US, so to hit the goal the country will have to deliver more doses sooner than this question implies. Still, the uptick in forecasters’ confidence is a good sign.

(The company doesn’t publish the details of how it aggregates forecasts but I’m told it involves a mix of weighting based on newness and a forecaster’s past accuracy, plus making the aggregate forecast more extreme under certain conditions. You can read more about common aggregation methods here and here.)

How many Americans will have received a dose

Good Judgment also has an open platform where anyone can make forecasts, and there’s a question up there about how many Americans will have received at least one dose by the end of March. Those forecasters are quite confident the number will fall between 90 and 105 million, with the most likely outcome falling between 95 and 100 million.

If you take the median of their most likely scenario, 97.5 million, that implies 31.5 million more people receiving at least one dose in the last 20 days of March—that’s just under 1.6 million new people per day, up from the 1.4 the US averaged in the seven days prior to this post. In other words, they expect the pace of vaccination to continue to increase modestly throughout the rest of this month.

On Metaculus, another forecasting platform, the median estimate is that the US will have given 100 million people at least one dose by April 2

Finally, there is one Metaculus question that tackles the Biden promise directly, asking whether there will be enough vaccine doses available for all US adults by the end of May. The median forecast there gives a 63% of that outcome. 

I haven’t gotten much into the why here, partly because it’s a Sunday, partly because part of the point is taking these estimates as a form of evidence in themselves. All in all, the picture is much more optimistic than a month ago and consistent with this piece that suggests the Biden target is reachable. It may even be more likely than not.

Disclosure: I sometimes forecast on these platforms under a pseudonym for fun, but I have no financial stake in any of the questions or in the platforms.

Note: I’ve been somewhat loose here about describing the forecasts. Part of me thinks I should be more precise about exactly what every forecast says, at least if it weren’t Sunday evening. But part of the point is trying to strike a balance between the rigorous precision of forecasting platforms and the kind of writing people in the wider world want to read. I’m definitely open to feedback.

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