statistical purposes (see Steffey and Bradburn, 1994). Thus, the plan and schedule for MAF have been designed to satisfy not only the needs of the 2000 census, but also the continuous measurement needs of the American Community Survey.1 From the viewpoint of the census alone, there are several benefits of a continuously updated MAF: it provides a smoother or more level work flow, avoiding huge precensus peaks that may be difficult to staff; it provides the opportunity for continuing partnerships with census participants and users, especially local governments; and it facilitates the use of quality control programs that should lead to a higher quality list.
With the innovations in methodology proposed for the 2000 census, the fundamental importance of an accurate MAF and TIGER database to the success of the census is significantly increased. As subsequent chapters illustrate, the offering of alternative means of response, the use of sample nonresponse follow-up, and the plans for integrated coverage measurement all depend on having a reliable dwelling list, referenced to correct geographic locations. For example, the matching of information coming from "Be Counted" forms to the census database requires complete and unambiguous address and geographic area identification. The success of both nonresponse follow-up and integrated coverage measurement is contingent on an accurate MAF with clearly identified dwelling units linked to the correct geographic locations. Although the quality of the initial lists was always important for the initial mail-out of census form, it takes on added importance with the introduction of methodology for the 2000 census. The quality of the initial MAF and its linkages to TIGER may well be the single most important factor determining the success of the 2000 census.
Parallel updating of the representation of geographic features in TIGER and of dwellings in MAF is not only necessary but efficient. Information sources that generate new addresses will often simultaneously generate geographic features, especially roads and streets, that must be added to TIGER, and vice versa. But equally as important as the current individual updating of TIGER and MAF is the currency of the linkage between them. In updating these sources in parallel, it is important to carefully manage their linkages and vintages. Since some census-taking tools (e.g., maps) are derived from TIGER, while others (e.g., address listings) are derived from MAF, the two databases must be properly linked. Addresses or features reflected in one but not the other, or maps and address lists coming from asynchronous versions of the two databases, can lead to confusion and loss of confidence by local government officials who are helping to improve these databases and by census field staff who are relying on them to take the census.