Re-asking the same consumption item requires wording that flags one answer for exclusion

Evidence

Double-Counting: It may sometimes be useful to create a cross-check by gathering data on the same items in more than one place in the questionnaire. In these cases, the questions should be worded carefully so that the analyst knows how to exclude one or the other to avoid double counting these data in the estimate of total consumption. — Gary Goertz, Social Science Concepts and Measurement, 241

Categorization

• SHARE: A nerdy survey-design gotcha worth sending to anyone who has built a household consumption questionnaire — redundant cross-checks silently inflate totals.