The SIPP has a number of advantages for studying material hardship. The Adult Well-Being Module covers many topics of interest, has been administered in three panels to date, and will presumably be included in future panels, so that comparisons in levels of hardship over time will be possible.
Furthermore, the SIPP collects rich economic and demographic information on sampled households for a period of up to four years. Information is collected on all members and they are followed to new locations if they move away either individually or as a group. This allows of changes in household composition to be tracked during the periods preceding and following the measurement of hardship, and the correlation of hardship measures with many household characteristics. The large sample size also permits subgroup analyses.
The Adult Well-Being Module is administered to one member in each household. A household is defined as the group of people living at a particular address at the time of the interview. This approach, however, introduces several possible sources of error. For example, consider the initial question of the Adult Well-Being Module:
- During the past 12 months, has there been a time when (YOU/YOUR HOUSEHOLD) did not meet all of your essential expenses?
To the extent that respondents have been members of multiple households during the past year, they may or may not report on the experiences of the household in which they now reside. Similarly, there may be new household members that the respondent knows little about.
These issues do not arise with respect to the durable goods and housing safety items, because they pertain to a point in time. The problems also are less severe for the food security battery, which refers to a relatively narrow window (four months) and allows the analyst to determine at least whether the household "had enough to eat" in each of those months.
The food security battery contains modified versions of some of the questions included in the full 18-question battery that appears in the Current Population Survey (CPS). The questions have been adapted from a 12-month period (as asked in the CPS) to a four-month period. The subset of questions included does not match the short version of six items currently recommended by the Census Bureau, in part because the subset was developed before research on the statistical properties of the full battery had been completed. Mark Nord of the Economic Research Service has developed an algorithm which maps responses to five of these items to the standard three-point food security scale: food secure, food insecure without hunger, food insecure with hunger.(9)
Because the SIPP sample frame comprises the non-institutionalized population, some forms of homelessness are not represented. Doubling up also may or may not be captured, depending on whether the householder considers those who moved in to be part of the household rather than visitors.