Derivation
Construction rule: for "daily-food" items all consumption recorded in the household diary book were summed by calendar day, binned into four 7-day bands (1-7, 8-14, 15-21, 22-end) and aggregated to produce week_1 .. week_4; their sum is total_all_weeks. For items originally reported on longer recall periods the raw payment was converted to a monthly equivalent: monthly items >> amount x 1; yearly items >> amount / 12; personal-transport (3-year) >> amount / 36. The column total_price is a convenience copy of total_all_weeks retained for compatibility with earlier PECS code. The total price is the actual total value according to its actual reference period.