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Survey Estimates of Wealth - Mathematica Policy Research

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Questionnaire design and interviewer training give the SCF an advantage over these other<br />

surveys as well. Measuring wealth is a major purpose <strong>of</strong> the SCF, and the oversampling <strong>of</strong> highincome<br />

families makes it cost effective to design questions and train interviewers to identify and<br />

distinguish among types <strong>of</strong> wealth that may be rarely seen in the PSID or the SIPP. Yet the<br />

success <strong>of</strong> the PSID (and, as we shall see, the HRS) with a brief wealth module embedded in a<br />

survey with much broader objectives would seem to suggest that the wealth focus is less<br />

important than other aspects <strong>of</strong> the data collection.<br />

Lastly, the comparatively low estimates <strong>of</strong> aggregate and mean wealth in the SIPP are<br />

influenced in part by topcoding, which is designed to protect the confidentiality <strong>of</strong> SIPP<br />

respondents but in so doing undoes some <strong>of</strong> the survey’s success in capturing the wealth <strong>of</strong> the<br />

wealthy. 22<br />

Neither the SCF nor the PSID topcodes its asset or liability amounts but relies on<br />

other methods <strong>of</strong> perturbing the data to protect confidentiality. We examine aspects <strong>of</strong> the role<br />

<strong>of</strong> each factor in Chapter IV, and we attempt to disentangle their relative contributions to the<br />

disparities observed between the SIPP and SCF estimates <strong>of</strong> wealth in Chapter V.<br />

We considered different approaches to measuring the shortfall in the SIPP’s estimates <strong>of</strong> the<br />

wealth <strong>of</strong> the wealthy. Removing the wealthiest one or two percent <strong>of</strong> families from each <strong>of</strong> the<br />

surveys is what we favored initially. But as Table II.7 makes clear, the top one or two percent in<br />

the SCF and the top one or two percent in the SIPP do not represent the same families. Rather,<br />

most <strong>of</strong> the families represented by the wealthiest one or two percent <strong>of</strong> SCF families are not<br />

represented in the SIPP at all. Screening on an absolute rather than relative level <strong>of</strong> net worth,<br />

22 The Census Bureau recently adopted a new rule to make topcoding consistent across its surveys—including<br />

the decennial census. Topcoding for all continuous fields will be set at either the 99.5th percentile, as measured<br />

among all persons, or the 97th percentile, among persons with nonzero values, whichever is higher. The 1996 SIPP<br />

panel may have used lower topcodes.<br />

30

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