History. 2 of 6: still nothing 31 days after the end of the year (Theresa May on social care 2017, Johnson on levelling up 2021, by two days).
Hunch. On 6 November no plan had been published, and the day before Andy Burnham had said there was no firm date for it.
The 31 January market resolves YES if the same plan, on the same test, is not on GOV.UK by 23:59 London time on 31 January 2027. BBC News and The Guardian settle it if GOV.UK does not open.
We looked for cases where a UK prime minister promised a major government document and said it would come by the end of the year. We found six, from 2012 to 2021. Three came out in time. In the other three nothing was out by 31 December.