A revised plan for the 2000 Decennial Census was announced in a 24 February 1999 Bureau of the Census publication and a press statement by K. Prewitt, Director of the Bureau of the Census. Census 2000 will include counts and ``adjusted'' counts. The adjustments involve complicated procedures and calculations on data from a sample of blocks, extrapolated throughout the country to demographic groups called ``post-strata.'' The 2000 adjustment plan is called Accuracy and Coverage Evaluation (ACE). ACE is quite similar to the 1990 adjustment plan, called the Post-Enumeration Survey (PES). The 1990 PES fails some plausibility checks and probably would have reduced the accuracy of counts and state shares.
ACE and PES differ in sample size, data capture, timing, record matching, post-stratification, methods to compensate for missing data, the treatment of movers, and details of the data analysis. ACE improves on PES in a number of ways, including using a larger sample, using a simpler model to assign ``match probabilities'' to records with insufficient data, and incorporating mail-back return rates into some post-strata. Nonetheless, ACE shares the most serious problems of PES. The ``Be Counted'' program, census response submission over the internet, computer unduplication of records, the treatment of movers, a new definition of ``correct address,'' more limited search for matching records, the use of optical character recognition (OCR) to capture data, the data collection schedule, and the assignment of ``residence probabilities'' to some sample records, are likely to make ACE less accurate than the 1990 PES.