felt you should because there wasn’t enough money for food,” “were you ever hungry but didn’t eat because you couldn’t afford enough food?”) This seems appropriate, because the experiences asked about seem unsuited to proxy reports; if “you” in these questions refers to the respondent, then it is inconsistent with the use of “you” as (probably) plural in other FSS questions. The experience of “worry” (“We worried whether our food would run out”) also seems unsuited to proxy reports, but it is asked about as though it is a household-level concept.

Reference Periods

A large body of empirical literature exists that examines the relationship between length of the reference period and the level of measurement error (see for example, Bound, Brown, and Mathiowetz, 2001). As noted by Schaeffer and Presser (2003), “The choice of reference period is usually determined by the periodicity of the target event, how memorable or patterned the events are likely to be, and the analytic goals of the survey.”

In principle, the 12-month reference period currently employed in the FSS allows researchers to estimate the proportion of households that experienced food insecurity in a year, a concept that encompasses seasonal variation. While the motivation to use a 12-month reference period is clear, evidence indicates that the reference period may be too difficult for respondents to implement accurately. For example, analysis of prevalence rates of food insecurity and hunger suggested a seasonality effect such that rates differed depending on whether the survey was fielded in the spring (April) or the fall (September) (Cohen et al., 2002). Although one might expect that episodes of severe food shortage or hunger would be salient and therefore memorable, it is possible that the occurrence of such events is salient, but their frequency, duration, or timing are not reported accurately. This could occur if episodes of hunger occur in stressful contexts that are not conducive to encoding these experiential features. Furthermore, episodes of severe food shortage or hunger (or of constrained resources) may have vague boundaries: it may be easy to say that a time of constrained resources has now become a time of hardship, but it may be difficult to pinpoint exactly when the character of the event changed. Such ambiguities may make it difficult to encode or enumerate events like times of hunger.

Two important issues regarding the reference periods included in the questions need to be addressed: (1) the appropriateness of using (for the most part) an annual reference period to evaluate food insecurity and (2) the best way to specify the reference period within the wording of the individual questions. Note that the FSS as administered to the respondent includes not only the 12-month reference period but also 30-day follow-up



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