COMPUTING SCIENCE
Machine Politics
Brian Hayes
Point-and-Click Redistricting
The computer is already an essential tool in redistricting; no state
today draws its districts with Magic Markers. The computer tools in
common use are interactive programs. You sit at a display screen
showing a state map that can zoom in on individual counties,
precincts or census tracts. You select a geographic unit on the
screen and then issue a command to assign it to a district or
transfer it from one district to another. The system offers
immediate feedback on the political and demographic consequences of
each move. You see at a glance the population of each district, its
racial and ethnic composition and various indicators of political allegiance.
Underlying this interactive facility is a database linked to the
map. Basic demographic data come from the Census Bureau, with
populations broken down into geographic units as small as the census
block, which generally comprises about a dozen houses. Political
intelligence-such as numbers of registered voters, party
affiliations, voter turnout statistics and the results of key
elections-has to be collected from county boards of elections. The
hardest part of building the database is reconciling data from
different sources. Boundaries of wards and precincts don't
necessarily coincide with the boundaries of census blocks, and so
interpolation is needed. (For the 2000 census, the states and the
Census Bureau are cooperating to make the boundaries more
consistent, which means the next census should be a more efficient
tool for the gerrymanderer.)
The introduction of computers into the redistricting process has
allowed more precise analysis of proposed plans. A map can be
fine-tuned by shifting individual census blocks from one district to
another, whether to equalize populations or to achieve political
goals. It is no accident that in many states both major parties have
access to their own computer systems for redistricting.
For the 1990 round of redistricting most states employed proprietary
software specially designed for the purpose and running on
mainframes or minicomputers. For the 2000 round there is growing
interest in adapting more versatile geographic information systems
to redistricting, and running them on client-server networks of
computers. But these systems too are mere interactive aids to the
human redistricter; they do not make autonomous decisions about
where to draw boundary lines.
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