quarters residents, who appear to have been poorly enumerated (see Section 4-F). Finally, a flaw in the planning for not only the A.C.E., but also the census itself, was the failure to anticipate the extent to which certain groups of people (e.g., college students, prisoners, people with two homes) would be duplicated in more than one census record (see Section 6-A.7).

Overall, the original A.C.E. was well executed in terms of timely and well-controlled address listing, P-sample interviewing, matching, follow-up, and original estimation. Although the sample size was twice as large as that fielded in 1990, the A.C.E. was carried out on schedule and with only minor problems that necessitated rearrangement or modification of operations after they had been specified. Mostly, such modifications involved accommodation to changes in the MAF that occurred in the course of the census. For example, the targeted extended search (TES) procedures had to be modified to handle deletions from and additions to the MAF that were made after the determination of the TES housing unit inventory (Navarro and Olson, 2001:11).

Some procedures proved more useful than had been expected. In particular, the use of the telephone (see Appendix E.2) enabled P-sample interviewing to begin April 24, 2000, whereas P-sample interviewing for the PES did not begin until June 25, 1990. All A.C.E. processes, from sampling through estimation, were carried out according to well-documented specifications, with quality control procedures (e.g., reviews of the work of clerical matchers and field staff) implemented at appropriate junctures.

The A.C.E. P-sample, partly because of design decisions made for the previously planned Integrated Coverage Measurement Program (see Section 5-D.1), included three groups of people and not two as in the 1990 PES. The three groups were: nonmovers who lived in a P-sample housing unit on Census Day and on the A.C.E. interview day; outmovers who lived in a P-sample housing unit on Census Day but had left by the A.C.E. interview day; and inmovers