really different from the participants for whom one can query both subject and proxy pairs? If people cannot report for themselves, how does one know what somebody else would really be reporting for them? Magaziner responded that he does not know empirically whether that would work. Should there be a subsample? Given currently available information, yes, it would be worthwhile. At least it would help with sensitivity analysis or setting some boundaries on what is learned.

For the oldest old, the proxy frequently is more accurate because in many cases people will underplay their disabilities because of fear of being moved from independent living to assistive living or a nursing home. Another factor is that the elderly person may report that he or she is independent if a caregiver is making activities feasible that would not otherwise be feasible.

Magaziner commented that the direction of the discrepancy becomes important in a population survey in which people of all ages are reporting. One wants to know about that 96-year-old person who cannot quite self-report because he or she does not understand the question. When he or she cannot give what a reasonable person would believe is a reasonable reply, one asks the proxy. Often researchers make simple substitutions, but maybe that is not what one wants to do. Researchers do not have an answer, but that is what needs to be addressed if they do not want to lose people in their attempt to obtain information about the whole population, and not just those who can provide an answer for themselves.

Should one be guided by the findings on the characteristics of the proxies associated with discrepancies in selecting people to serve as proxies? The answer is yes, if one can find the perfect proxy. One has to work with what is available in the real world. The choice may be dependent on the question to be asked, and who has the best opportunity to observe the subject? For example, in a nursing home, perhaps the family proxy is not the best person but someone who sees the subject all the time on a daily basis.

In closing, Andrew Houtenville (New Editions Consulting) informed the participants about two research efforts under way—one led by Mathematica Policy Research and the other by New Editions Consulting, both funded by the National Institute on Disability and Rehabilitation Research, and both about proxy response. Mathematica is going to be working on the question of what protocol is best for a given situation, using an experimental design. New Editions Consulting is going to look at administrative data as a third source of information. Work has been done on this by some economists at the National Bureau of Economic Research using Canadian data in the reporting of diabetes in a working-age population. That work did not involve proxies, but it gave the degree of reliability of reporting diabetes as well as an association with the reporting of a work limitation among the working-age population.



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