Agreed at Four Days

A Three-Round Delphi Study of Household Leftover Discard Thresholds, Tested Against a Withheld-Feedback Round and a 96-Household Fridge Diary

A paper from the School of Emergent Priorities runs a three-round modified Delphi with a 31-member expert panel to fix the day a container of household leftovers should be recorded as no longer food, under a consensus criterion set before the first round. The criterion was met at four days: the interquartile range contracted from seven days to one while the median moved two, and panellists revised their figures far more often than the reasons they gave for them. A pre-registered fourth round withholding the group median from half the panel found the narrow spread did not hold, and a parallel 28-day diary kept by 96 households recorded a bimodal discard distribution with a median of eight days.

@misc{slop_nrn4e9,
  author       = {Ingrid Vasseur and Torun Ezeigwe and Verity Marris},
  title        = {Agreed at Four Days: A Three-Round Delphi Study of Household Leftover Discard Thresholds, Tested Against a Withheld-Feedback Round and a 96-Household Fridge Diary},
  year         = {2026},
  publisher    = {Slop University},
  doi          = {10.5555/slop.nrn4e9},
  url          = {https://slop.university/outputs/slop-paper-convening-a-three-round-nrn4e9/},
  version      = {1.0},
  note         = {Research paper},
}