were produced for many more groups—called post-strata—than are summarized here; see “A.C.E. Operations,” below.3) The A.C.E. estimates apply to the household population; they exclude people in institutional and noninstitutional group quarters (e.g., dormitories, prisons, nursing homes, group homes), for whom coverage is not estimated and who therefore, by default, are assumed to have zero net undercount.4 People living in remote Alaska and people enumerated in shelters are also not included in the A.C.E. The PES estimates include people in noninstitutional group quarters, but there are no separate estimates for them.

Overall, the population was undercounted by 1.2 percent in 2000 as estimated by the A.C.E., less than the net undercount rate of 1.6 percent estimated for 1990 by the PES. The 2000 and 1990 estimates of net undercount show similar patterns, in that net undercount rates are significantly higher in both censuses for most minority groups than they are for the white or some other races (not Hispanic) category. However, the 2000 net undercount rates for Hispanics and non-Hispanic blacks are significantly lower than the rates in 1990: for 2000 they are estimated as 2.9 percent and 2.2 percent, respectively, compared with estimates from 1990 of 5 percent and 4.6 percent, respectively. The net undercount rates for the white or other races category are the same in both censuses, 0.7 percent.

By age and sex, net undercount rates in 2000, as in 1990, were higher for men than women. Net undercount rates were also higher in both censuses for younger people than for those aged 50 and over, for whom there is a small estimated net overcount. The most pronounced difference in net undercount rates by age between 1990 and 2000 is for children under age 18, for whom the rate is significantly lower in 2000 (1.5%) than it was in 1990 (3.2%).

By housing tenure, people who rent continued to be undercounted at a higher rate than people who own their homes, but the net undercount rate for renters is significantly lower in 2000 compared with 1990. For owners, the net undercount rate is estimated at less than 0.5 percent in both censuses; for renters, the estimated net undercount rate is 2.8 percent in 2000, compared with 4.5 percent in 1990.


In census terminology, the racial and ethnic groupings used in defining post-strata are called domains. They are carefully defined in a hierarchical manner (due to the option to report more than one race; see Table 6-2), and may differ from colloquial definitions of a particular racial/ethnic group.


This assumption needs evaluation since people in group quarters are estimated to be 2.8 percent of the total population (see Chapter 4).

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