A structured way to show the working behind a prevention claim — what the money buys, how that changes risk, what it could avoid, who pays and who benefits, and how good the evidence is at every step.
The Ledger does not calculate the value of an outbreak that never happened. It records the chain of evidence and assumptions required to estimate it — investment, capability, risk change, outcomes, economic consequences — across low, central and high scenarios, and it never shows a ratio without them.
The methodology note explains the eight steps, how the calculation works, how to read the results and the mistakes that most often distort prevention claims. A first worked case — mass dog vaccination for rabies control in Ethiopia — is set out in What Does Prevention Actually Buy?
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Download the workbook (Excel, v1.0) Download the worked example
Version 1.0, released September 2026. An experimental research tool, released to be used, tested and challenged — not a substitute for a full economic evaluation where one is required.
Results update as you type. You can export your assessment to Excel or print it to PDF. For larger assessments, or to keep a version history, use the workbook.