While the data was being assembled, Dickinson created and tested the Graphical User Interface (GUI) for the redistricting application. The primary considerations were that the program be easily understandable to council members and their aides, that it display immediate demographic changes in response to district boundary moves, and that it conform to city redistricting guidelines.
Dickinson designed the GUI to immediately display the results of district boundary changes geographically as well as through bar charts, pie charts, tables and a histogram indicating the degree of deviation from the ideal population configuration.
Dickinson linked the population data, provided by the planning department in DBF format, to the polygon shape files of census blocks, the latter being color-coded by district. To ensure boundary changes remained within city guidelines for redistricting, she also programmed the application to prevent the splitting of census blocks, moving council members out of their respective district, or putting together or breaking up districts with a minority majority.
Seeing the Options
Council members were allowed to develop up to five separate redistricting plans each for discussion. Out of these, members would select several for presentation to the City Council. Approved plans would then be open for discussion at a public hearing.
Since the application immediately and graphically displays the effects of boundary changes on the population and ethnic composition of a particular district, members were able to quickly explore a range of redistricting plans. The steps are fairly straightforward and the results of boundary changes immediately available. For example, if a district boundary is moved to include two adjacent census blocks, the newly acquired blocks assume the color coding of that district.
The program then recalculates the resulting changes in population and ethnicity, and indicates how close the district is to the ideal configuration. Council members can also click on a census block outside their respective boundaries and see its demographic makeup before moving the block into their district. The ability to quickly generate "what if" options helped members determine those redistricting plans most likely to be approved by other members, the City Council and the public.
Throughout the process, however, boundary adjustments had to be small because changes to a district also affected the surrounding districts.
The GIS staff trained council members and their aides in half-hour sessions for each group. After that, two-hour time slots on the application were allocated to each group for developing their respective plans. According to Dickinson, plans for all nine districts were completed within a week.
"This wasn't just for their own districts; council members had to come up with five plans for the readjustment of all districts." She said the process was an eye-opener for many council members. "They had an intuitive idea of the ethnic breakdowns of their respective districts, but some of them were in for a surprise when they incorporated census blocks into their districts before checking them out."
Dickinson said that after development of the individual plans, council members had to convince others that theirs was the plan to go with. "There was a lot of discussion and compromising. If a member liked another's plan except for one or two points, they would do minor tweaking until both were satisfied. Those who didn't need to make any plans agreed with the ones developed by others. In the final phase, council members came up with three different plans and voted on them. Open hearings resulted in general public approval of the final redistricting plan."
"It was an elegant application," said Humphrey. "Simple, easy to use and totally interactive. We tried to make it as open and understandable as possible. As a result, we did the redistricting process in just over two weeks. The public was generally accepting of the plan, mainly because there were no dramatic changes in the borders. The 1996 redistricting plan produced zero litigation."
Bill McGarigle is a writer, specializing in communications and information technology. He is based in Santa Cruz, Calif. E-mail