On 29 September 2023, I spoke at the Australian Evaluation Society’s annual conference on what policymakers can learn from health. The speech began with the example of the radical mastectomy, a procedure that was needlessly performed on half a million women before a randomised trial revealed the truth. The text is available at https://ministers.treasury.gov.au/ministers/andrew-leigh-2022/speeches/address-australian-evaluation-society-2023-international