So, people who participated in the census by completing a form or by speaking with an enumerator, will be removed from that count for statistical reasons, not because they moved away or died. The paradox is that in attempting to make the actual count more accurate by an adjustment, we might be making the shares less accurate. The shares are very important because they determine how many congressional seats each state gets, how political representation is allocated within states, and how large a 'slice of the pie' of federal funds goes to each city and state. Any upward adjustment of one share necessarily means a downward adjustment of another. Because there is a loser for every winner, we need solid ground to stand on in making any changes.
Statisticians disagree about how solid the ground is.
They are skeptical about the dual system estimator because errors in the PES may account for half of the undercount. Lastly, they criticize the method for ignoring variability in undercount rates from one geographic area to another. If all goes as planned, the 2000 census will be the first decennial census to produce two sets of numbers. This historic step is not necessary. The census is not that badly broken, though the error is not easy to measure.