frequently purchased items. They find that each additional day of recall results in about 3 percentage points decline in reported daily expenditure.<sup>8</sup> Other experiments on recall period that were identified are all based on surveys in which the same household reports expenditures across two different recall periods _within_ the same survey. This is potentially problematic if there is conditioning bias due to households or interviewers imposing consistency between their responses.<sup>9</sup> Grosh et al _._ (1995) compare consumption estimates from the Ghana LSMS reported by short (2-week) recall periods and longer recall. The latter were “explicitly normative” questions in which households report the number of months purchases were made in the last year, how often they were made, and how much was usually spent each time (referred to here as “usual-month” questions). While food expenditures were not different, non-food expenditures were 72 percent higher based on short recall, contrary to expectations. Similar analysis is presented for Jamaica (Grosh et al _._ , 1995), Côte d’Ivoire, Vietnam, and Pakistan (Deaton and Grosh, 2000). Deaton and Grosh (2000) conclude that there is only a slight sensitivity to the choice of these recall periods. In much earlier work from Malawi in 1970, Plewis (1972) presents admittedly weak evidence that 7-day food recall is consistent with 24-hours recall (in some sense, this is like a diary). However, it is not clear to what extent conditioning bias is driving these results. The Indian National Sample Survey (NSS) experimented with using a “last week” versus a “last month” recall and found that for the all-food aggregate the estimates based on weekly recall were 21 percent higher (NSSO 2003).

In short there are numerous features of survey design that can result in different reported consumption for the same household over the same period of time. Usually based on ad hoc or opportunistic studies, clear divergences arise in measured consumption when recall periods are varied, commodity lists are shortened or lengthened, and consumption is recorded through diary or recall. Underlying these divergences are different magnitudes of various reporting errors, thus making it unclear (i) which variant of consumption measurement more closely hews to the truth; (ii) the implications of survey design for subsequent analysis, especially when consumption measures derived from different variants are combined in the analysis; and (iii) generalizable lessons for future consumption measurement in developing country surveys. The current study was designed to shed light on all three questions.

> 8 Dutta Roy and Mabey (1968) present results of studying alternative recall periods in Ghana for experiments circa 1966; they found significantly larger declines in reported expenditure than Scott and Amenuvegbe (1991). They attribute this to a combination of memory lapse for longer recall periods and over stated expenditures for short recall periods, although it is not clear how this conclusion is drawn.

> 9 A related research design would be to collect both diary and recall consumption data from the same household. Ahmed et al. (2006) study food expenditure among Canadian households reported by recall (past one month) and then collected for the following 2 weeks by diary. However, this design also risks cross-module spillovers within the household.