Reproduction of Scientific Basis for “Reducing Contact by 80%†(Reappraisal)

Yasushi Iwamoto

No CIRJE-J-315, CIRJE J-Series from CIRJE, Faculty of Economics, University of Tokyo

Abstract: This paper aims to reproduce the results of the mathematical model of infectious diseases that provided the scientific basis for the “Reducing Contacts by 80%,†which was one of state of emergency measures in the spring of 2020. Since some results were successfully reproduced from publicly available information, the overall calculations were correct. However, when examined within an SIR framework that explicitly models the mechanism generating new infections, the published figures swapped new infections and the stock of infected individuals. The figures are inconsistent with both the model deriving the damage estimates and the theoretical rationale for contact reduction as a policy instrument—namely, that reducing contact lowers the number of new infections. As a result, the analysis of countermeasures of COVID-19 lacks internal validity. While this paper does not address the real-world validity of the model, it is “incorrect†scientific advice in the sense that it lacks internal validity. To avoid similar situations in the future, it will be necessary to have a system in place to check the analysis by a larger group of experts.

Pages: 46 pages
Date: 2026-02
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Persistent link: https://EconPapers.repec.org/RePEc:tky:jseres:2026cj315

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