(March 2001) A.C.E. underestimated duplicate enumerations in the census and correspondingly overestimated correct enumerations. It also overestimated P-sample Census Day residents, particularly nonmatches. The net effect (assuming an accurate estimate of omissions) was to overstate the correct enumeration rate, understate the match rate, and overstate the DSE estimate of the population by about 6.3 million people. Correcting this overstatement (before an adjustment for undercounting of men relative to women) would have produced an estimated net overcount of the population of 3 million people or 1.1 percent of the household population (see U.S. Census Bureau, 2003c:Table 12; see also Sections 6-B and 6-C.2).
The A.C.E. (and PES) involved a two-stage matching process. The first stage of matching occurred after P-sample interviewing; it began with a computer match followed by a clerical review of possible matches and nonmatches in order to establish an initial match status (P-sample) or enumeration status (E-sample) for as many cases as possible. The second stage occurred after follow-up of specified nonmatched and unresolved cases to try to resolve their status using additional information from the follow-up interviews. The accuracy of the matching can be no better than the accuracy of the underlying data about household composition and residence (as discussed in Section 6-A.7). Assuming accurate information, the question is the quality of the matching itself.
Examination of data from the original (production) A.C.E. matching provides indicators that the quality was high. Specifically, initial match status codes were rarely overturned at a subsequent stage of matching: clerks confirmed a high percentage (93 percent) of computer-designated possible matches as matches; technicians and analysts who reviewed clerical matches rarely overturned the clerks’ decisions, and field follow-up most often confirmed the before-follow-up match code or left the case unresolved.7 Because of the dependent nature of the production matching, however, such