A number of researchers have developed material hardship indexes that combine hardships into one single measure. These indexes all define hardship in terms of direct measures of families' experiences and actual living conditions, and they all include a core set of basic needs and food security indicators. However, there is considerable variability in the number and types of indicators included in the various indexes. Even in cases where all studies use the same basic indicator, researchers use different questions and combinations of questions to construct these indicators. Although many researchers have used data from the Survey of Income and Program Participation (SIPP) in their hardship indexes, not much is known about whether these measures are valid measures of material hardship among families with children and how they should be combined to form a hardship index.