report the consumption of Tubers, the 7- and 14-day long list recall designs (modules 1 and 2) report a significantly lower consumption incidence of 58–59 percent. The only food group reported at the same frequency as the benchmark is Vegetables; two food groups, Oils/Fats and Beverages, are actually reported at a significantly higher incidence of 5–6 percentage points. These two exceptions are true only for the long list recall modules. The 7-day subset list and collapsed list (modules 3 and 4) underreport the consumption of all food groups. Indeed, the downward bias in incidence is even larger in magnitude for the 7-day subset and collapsed lists. For example, Tuber consumption incidence is estimated at 52 percent–54 percent. While the consumption incidence of the 7-day short list may be expected to be lower than the 7-day long list because the former module design asks about a fewer number of individual food items, there is no prior expectation that the 7-day collapsed list will record lower consumption incidence. The fact that the collapsed list does record a lower incidence for all food items suggests that important consumption items are excluded because of a lack of cognitive prodding that the longer list explicitly incorporates in the design.

By contrast with the other recall modules, the usual month approach to recall survey design reports significantly higher consumption incidence among almost all food groups, with the sole exception of Cereals, which are consumed by 96 percent of the benchmark households. This difference most likely derives from the different cognitive demand of considering a usual month, which apparently prompts respondents to report significantly higher consumption incidence relative to the actual consumption recorded in the benchmark. Finally, the two household diary modules (modules 6 and 7) tend to report lower consumption incidence among various food groups such as Fruits (9 percent lower) and Meals Outside the Home (7 percent–9 percent lower). While the frequency of the household diary supervision does not appear to influence the accuracy of consumption incidence measurement because the rates are equal for the weekly and thrice-weekly supervised diaries, the two household diaries systematically record lower incidence relative to the personal diary.

Overall, these results show that an important component of recall error is the omission of any positive value of consumption for particular items. It is possible that a portion of this error arises because of personal leave out error, whereby the household respondent likely misses some individual consumption. However, because the magnitudes of the incidence shortfall are relatively high for all recall modules (except the usual month) and occur even in the case of nearly universally consumed items such as cereals, this indicates that a key channel for recall error is complete forgetting (or deliberate suppression).<sup>12</sup> By contrast, the usual month approach prompts households to report a far higher monthly incidence of consumption than the benchmark, suggesting a different pattern of reporting error in this module. Given that the hypothetical nature of the 12 That the 7-day recall tends to report lower consumption incidence than the 14-day recall may, in principle, arise because of the less diversified actual consumption in a one-week period relative to a two-week period. However, the 7-day recall reports relatively lower incidence than the 14-day recall for those selected food groups in a nonlinear fashion (going against expectation if the lower incidence derives solely from less frequent consumption across weeks). The conclusion that the lower reported incidence in the 7-day recall is largely driven by recall error of greater magnitude (relative to the 14-day recall) is supported by a comparison of the 7-day recall module with the consumption incidence recorded in the first week of the personal diaries. The shortfall in incidence is largely the same relative to the first week of the personal diaries as with both weeks. It is impossible to conduct a similar analysis for the usual month as the personal diary was only collected for a two-week period. Nonetheless, combining personal diaries from two households fielded within the same calendar month can simulate consumption incidence over a one-month period. This exercise also reveals higher reported incidence by the usual month than in the personal diaries, suggesting that a significant portion of the higher consumption incidence in the usual month arises because of response error.

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