How to Interpret Covid-19 Predictions
Reassessing the IHME’s Model
The IHME Covid-19 prediction model has been one of the most influential Covid models in the United States. Early on, it received heavy criticism for understating the extent of the epidemic. I argue that this criticism was based on a misunderstanding of the model. The model was best interpreted not as attempting to forecast the actual course of the epidemic. Rather, it was attempting to make a conditional projection: telling us how the epidemic would unfold, given certain assumptions. This misunderstanding of the IHME’s model prevented the public from seeing how dire the model’s projections actually were.
Adams, Jimi. 2020a. “Projections vs. Predictions, Redux.” Medium, 1 September 2020. https://jimi-adams.medium.com/projections-vs-predictions-redux-3d75eca07f4b/.
Adams, Jimi. 2020b. “What Are COVID-19 Models Modeling?” The Society Pages, 8 April 2020. https://thesocietypages.org/specials/what-are-covid-19-models-modeling/.
Cancryn, Adam. 2020. “How Overly Optimistic Modeling Distorted Trump Team’s Coronavirus Response.” Politico, 24 April 2020. https://www.politico.com/news/2020/04/24/trump-coronavirus-model-207582/.
IHME (Institute for Health Metrics and Evaluation). 2020. “COVID-19 Projections Assuming Full Social Distancing through May 2020.” Version of 8 April 2020. https://web.archive.org/web/20200408105853if_/https://covid19.healthdata.org/united-states-of-america.
IHME (Institute for Health Metrics and Evaluation) Covid-19 Health Service Utilization Forecasting Team and Christopher J.L. Murray. 2020. “Forecasting Covid-19 Impact on Hospital Bed-Days, ICU-Days, Ventilator-Days and Deaths by US State in the Next 4 Months.” MedRxiv preprint. https://doi.org/10.1101/2020.03.27.20043752.
Keyfitz, Nathan. 1972. “On Future Population.” Journal of the American Statistical Association 67, no. 338: 347–63. https://doi.org/10.2307/2284381.
Kirtman, Ben, Scott B. Power, Akintayo John Adedoyin, George J. Boer, Roxana Bojariu, Ines Camilloni, Francisco Doblas-Reyes et al. 2013. “Near-Term Climate Change: Projections and Predictability.” In Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change, 953–1028. Cambridge: Cambridge University Press.
Parker, Wendy. 2020. “Model Evaluation: An Adequacy-for-Purpose View.” Philosophy of Science 87, no. 3: 457–77. https://doi.org/10.1086/708691.
Piper, Kelsey. 2020. “This Coronavirus Model Keeps Being Wrong: Why Are We Still Listening To It?” Vox, 2 May 2020. https://www.vox.com/future-perfect/2020/5/2/21241261/coronavirus-modeling-us-deaths-ihme-pandemic/.
Saltelli, Andrea, Gabriele Bammer, Isabelle Bruno, Erica Charters, Monica Di Fiore, Emmanuel Didier, Wendy Nelson Espeland et al. 2020. “Five Ways to Ensure That Models Serve Society: A Manifesto.” Nature 582, no. 7813: 482–84.
Schroeder, S. Andrew. 2020. “How Many Have Died?” Issues in Science and Technology, 5 November 2020. https://issues.org/covid-19-pandemic-deaths-excess-mortality/.
Tufekci, Zeynep. 2020. “Don’t Believe the COVID-19 Models.” The Atlantic, 2 April 2020. https://www.theatlantic.com/technology/archive/2020/04/coronavirus-models-arent-supposed-be-right/609271/.
White House. 2020. “These 30 Days: How You Can Help.” 2 April 2020. https://www.whitehouse.gov/articles/these-30-days-how-you-can-help/.
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