produced from the TIGER data base would contain some 
errors of the type described above, they also knew that 
the training the enumerators would receive and the 
procedures the enumerators were being asked to follow 
provided the guidance necessary for them to annotate 
the maps with any needed corrections. In this way, the 
maps they would use to conduct the 1990 census would 
overcome any TIGER data base deficiencies that might 
otherwise have affected enumeration accuracy. 
Current Update Process 
The Census Bureau modified its update plan when 
many data users expressed strong interest in having 
maps that displayed the enumerator-noted corrections at 
the time local officials performed their review of the 
preliminary 1990 census housing unit and group 
quarters population counts at the census block level, 
scheduled for summer 1990. In addition, these data 
users expressed strong interest in having the correc 
tions appear on the maps and in the TIGER/Line files 
when they began to use them in conjunction with the 
final 1990 census data products. The Census Bureau 
was able to undertake this unplanned task because it 
still had the original graphic terminals used to build the 
TIGER data base after it received the new graphic work 
stations that would be their eventual replacements. At 
this juncture, the Census Bureau decided to enter not 
only the enumerator-noted corrections, but also those 
map corrections submitted by local officials during the 
fall of 1989 and the winter/spring of 1990. 
By updating the TIGER data base for the postcensus 
phase of the Local Review Program, the Census Bureau 
can produce maps that more correctly depict the 
features that the field staff saw as they completed their 
data collection rounds. These same improvements in 
map content will benefit all other users of the maps and 
the TIGER/Line files as well -- market researchers, 
election redistricters, delivery routing managers, 
emergency service responders, and so forth. 
The Future 
To prepare for the future and the ongoing maintenance 
of the TIGER data base, the Census Bureau is partici 
pating in several experimental programs with other 
Federal agencies and some state governments to 
evaluate possible methodologies for updating the feature 
and geographic entity information. The Census Bureau 
also is looking at these potential cooperative arrange 
ments as a way to improve the positional accuracy of the 
coordinate information in the TIGER data base through 
automated matches with more accurate local data sets. 
The approach finally selected probably will be some 
combination of cooperative programs and traditional 
approaches involving comparisons of paper maps. 
CONCLUSIONS 
All the foregoing make better understanding a very real 
possibility: The TIGER data base; the demographic, 
economic, and agricultural statistics available from the 
Census Bureau; the geographically referenced infor 
mation maintained by state and local governments, 
academic institutions, and commercial firms; and, the 
analytical power GIS technology makes available to 
study the interrelationships of these massive and diverse 
data sets. 
For those who wish to learn more about the background 
leading to development of the TIGER System, the map 
products prepared to support the 1990 decennial census, 
and the other “public” products the Census Bureau 
plans to make available during the next 18 months, a list 
of references follows the numbered notes. 
NOTES AND SELECTED REFERENCES 
1 Officially, “the United States” consists of the 50 states 
and the District of Columbia. For each census, the 
Census Bureau makes extensive data tabulations 
available for the United States and several statistically 
equivalent entities (see Notes 2-5 for the details of each 
recent census); the other areas often are referred to 
collectively as “Puerto Rico and the Outlying Areas.” All 
information in Figure 1 refer to the number of entities 
within these sets of “states.” 
The TIGER data base includes — on an equal basis — the 
1990 census set of states plus: 
• The Federated States of Micronesia and the Marshall 
Islands (which together comprise the balance of the 
former Trust Territory of the Pacific Islands). The 
Census Bureau included these entities in case it was 
asked to assist in conducting a census in these areas. 
• The Midway Islands. The Census Bureau included 
the Midway Islands to completely cover the area 
included within the boundaries of the State of Hawaii. 
Most references to “the United States” in this paper 
include the entire set of entities discussed above, 
including the ones in which the 1990 census has not 
been taken; if the latter entities were included in 
Figure 1, the counts would be: 60 “states,” 3,286 
“counties,” 60,600 E county subdivisions and places 
(including 30,560 e MCDs, 186 sub-MCDs, and 4,537 E 
CDPs), 61,600 E census tracts/block numbering areas 
(having 141,300 e tabulated parts), 229,200 E block groups 
(having 353,200® tabulated parts), and 7,012,500® blocks. 
2 In addition to the 50 states and the District of Colum 
bia (the United States), the 1980 decennial census includ 
ed American Samoa, Guam, the Northern Mariana 
Islands, Puerto Rico, the Trust Territory of the Pacific 
Islands, and the Virgin Islands of the United States. 
3 In addition to the 50 states and the District of 
Columbia (the United States), the 1990 decennial census 
includes American Samoa, Guam, the Northern 
Mariana Islands, Palau, Puerto Rico, and the Virgin 
Islands of the United States. 
4 In addition to the 50 states and the District of 
Columbia (the United States), the 1987 economic 
censuses included Guam, the Northern Mariana 
Islands, Puerto Rico, and the Virgin Islands of the 
United States. 
5 In addition to the 50 states (the United States, as 
there is no agriculture census taken in the District of 
Columbia), the 1987 Census of Agriculture included 
Guam, Puerto Rico, and the Virgin Islands of the 
United States. The Census Bureau is conducting agri 
culture censuses for American Samoa and the Northern 
Mariana Islands in conjunction with the 1990 decennial 
census of those entities. 
6 In addition to the county-level entities comprising the 
included states, the 1987 economic censuses tabu 
lated data for the seven offshore areas listed below as the 
statistical equivalents of counties: 
Alaska 
California 
Louisiana 
Texas 
Atlantic 
Northern Gulf of Mexico 
Pacific 
7 The 1987 Census of Agriculture tabulated data for the 
county-level entities comprising the included states with 
the following exceptions: 
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