Scaling Counties in a Checkerboard State

Scaling Counties in a Checkerboard State

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Jan. 24, 2004

Iowa county map
Iowa county map

A caucus is a closed meeting of equals, the word probably derived from the Algonquin cau-cau-asu, translated as “proponent” or “advisor.”

At 6:30 pm on January 19th, Iowa’s 1,993 precinct caucuses were called to order, beginning the first step of an elaborate six-month process:

  • In January, precinct caucuses choose precinct delegates to the county caucuses.
  • In March, county caucuses elect 3,000 state delegates to the state convention.
  • In June, the state delegates choose 16 delegates to the Democratic National Convention.
  • In July, Iowa’s 16 delegates vote for a presidential nominee.

How many precinct delegates?

To make things confusing, the Iowa Democratic Party does not release the number of precinct delegates chosen on the 19th. Instead, the party releases a tally of state delegate equivalents, an estimate of the results of the county caucuses that will be held in March.

Although the count of state delegate equivalents is at least two steps removed from the actual votes cast by caucus attendees, the count is about as close as we can get to actual voting data, and deserves some study.

A checkerboard state

Iowa caucus county results
County results
(Redrawn from a map appearing on the Des Moines Register’s web site)

Iowa caucus county results for John Kerry
County results for John Kerry
(Percentage won)

Iowa is an interesting state because its 99 counties are all roughly the same size and shape.

Published maps of the Iowa caucus results tend to use a county map marked with different colors for each candidate. For example, the map at right shows the first place finisher in each county, with split fields of color indicating two- and three-way ties. The overall visual impression is of a fairly even statewide split between Kerry (light gray) and Edwards (light red), with Dean (dark red) winning only a small number of counties.

County maps can also be drawn for individual candidates. At lower right, a map of county-by-county results for John Kerry shows the percentage of support he has received from each county. Kerry appears to enjoy broad support across the middle of the state, with strong support along the west and east borders, and weak support in the south.

Although both of these maps display accurate county data, and each county has roughly the same visual weight, there is a catch: the overall impression of each map is accurate only if each county elects an equal number of state delegates.

Scaling counties

Iowa county map

Guthrie and Polk counties

Guthrie and Polk counties, Iowa

Guthrie and Polk counties

In other words, with 3,000 state delegate equivalents and 99 counties, displaying state results on a county map of Iowa only works well if every county chooses roughly 30 delegates, or 1% of the state total.

In reality, the number of state delegates elected by each county varies widely. Polk county elects 430 delegates (a full 14% of the state total), while Guthrie county elects only 12 delegates (0.4% of the state total). The two counties have similar surface areas, but a 35-fold difference in their share of state delegates.

The reason for the difference is that state delegates are allocated according to population. Iowa’s estimated population in 2001 was just over 2.9 million, and with a population of only 11,323, Guthrie county does indeed represent only 0.4% of the state. Polk county contains the state capital and has a population of 379,029, or 13% of the total state population.

Iowa county map

Guthrie and Polk counties

Guthrie and Polk counties, Iowa

Guthrie and Polk counties scaled in proportion to their number of state delegates

Scaling each county relative to the number of delegates it elects produces a more accurate visual weighting (at right), though Polk county has broken its boundaries relative to the rest of the state, and Guthrie county has shrunk to a fraction of its former size. Although my previous attempts at mapping votes by county in the 2003 California Statewide Special Election scaled counties while maintaining most internal borders, Iowa’s gridlike pattern of counties makes it difficult to maintain internal borders without massive distortion. Another method of scaling is needed.

A framework of counties

One technique to reduce distortion is to modify the presentation of the county borders. Plotting the midpoint of each county and then drawing connections through shared county borders creates a simple network diagram of counties:

Iowa county framework

1. Plot county midpoints

Iowa county framework

2. Connect counties along shared borders

Iowa county framework

3. Remove county borders

Iowa county framework

4. Scale counties

Iowa county framework

5. Remove midpoints

Now when a county scales it has a flexible framework in which to move. Although county size is distorted, the relationships between adjacent counties are preserved.

A revised county map

Iowa county map

Guthrie and Polk counties

Counties scaled in proportion to their number of state delegates

Scaling all 99 counties in a similar way produces the revised county map of Iowa at right, shown at a scale of roughly 4 green pixels per state delegate (the enlarged map is more accurate, at roughly 25 pixels per delegate). For easier comparison, all counties are drawn as squares.

Although this map is not intended as a display of population, state delegates are distributed in proportion to population, and there is a correlation of about 974 people for every state delegate, or roughly 250 people for every green pixel (about 40 people per pixel in the enlarged map).

One advantage of this presentation is that the relative voting power of each county is made immediately apparent: the bulk of the state delegates are elected by the more populous central and eastern counties.

Iowa caucus county results

No scaling, no distortion

Iowa caucus county results

Distortion due to county scaling

Another interesting feature of this type of map is that any underlying graphical distortion of the state is made visible by comparing the before and after framework maps.

Scaled county results

Redrawn maps for county-by-county results and for John Kerry’s individual results are shown at right.

Iowa caucus county results

County results

Iowa caucus scaled county results

Scaled county results

Although less colorful, the redrawn maps may present a more accurate overall impression of statewide trends.

Iowa caucus county results for John Kerry

County results for John Kerry

Iowa caucus scaled county results for John Kerry

Scaled county results for John Kerry

Scaled individual results

Similarly, generating maps for individual candidates can reveal patterns of support not visible in traditional county-by-county maps.

Iowa caucus scaled county results for John Kerry

John Kerry: 38%
(1,128 delegates)

Iowa caucus scaled county results for John Edwards

John Edwards: 32%
(957 delegates)

Iowa caucus scaled county results for Howard Dean

Howard Dean: 18%
(540 delegates)

Iowa caucus scaled county results for Richard Gephardt

Richard Gephardt: 11%
(318 delegates)

Iowa caucus scaled county results for Dennis Kucinich

Dennis Kucinich: 1%
(39 delegates)

Iowa caucus scaled county results for Wesley Clark

Wesley Clark: 0.1%
(3 delegates)

 

Sources

  1. Des Moines Register
    Iowa Caucus Results
    DesMoinesRegister.com (January 20, 2003)
  2. Iowa Democratic Party
    Iowa Delegate Selection and Affirmative Action Plan for the 2004 Democratic National Convention
    IowaDemocrats.org (August 2003)
  3. U.S. Census Bureau
    State and County QuickFacts for Iowa
    Census of Population and Housing (2000)