There is someone out there who occasionally posts economic or political analysis of events in Idaho at a site called interstices.tumblr.com.  I don’t know who this person is, but they usually provide pretty sound, data-driven analysis on some interesting topics—a welcome relief from the unsubstantiated blather which often shows up on such sites. About 15 months ago this person looked at the July 2006 census estimates by county, and made what I thought were some interesting observations.  You can see them here.

But now we have updated estimates from July 2008, so I thought we’d piggyback on interstices’ earlier discussion, updating the analysis and adding a few other bits of information.

1.The most recent total state population estimate is 1,523,816. The following discussion is based on that number, realizing there will probably be a small (very small) increase by the time the official census figures are released.  The current estimated population is about an 18% increase since the last census so any city, county or legislative district would need to have a population increase of 18% just to keep up.  

2. There are 35 legislative districts, so the “ideal” population per district will grow to about 43,357 which is more than 6,300 people more per district than the 37,000 in each district after the 2000 census.  

3. While the ideal population per district is 43,357, the U.S. Supreme Court is pretty consistent in allowing some leeway here.  The general rule is that districts can be about 5% above or below the ideal population.  This allows a state to balance population equality with other factors like keeping county or municipal boundaries intact.  Thus, the acceptable range for legislative districts will be something like 41,361 to 45,713 (that’s 43,357 +/- 5%).

4. It is no surprise that a few counties dominated the growth rates: Ada (80,000 new residents, 27% growth rate since 2000); Canyon (52,000; 40%) and Kootenai (29,000; 26%).  These three counties account for 70% of the entire state population growth.  A few others showed more modest growth: Bonneville (17,000; 20%); Madison (10,000; 36%) and Twin Falls (10,000; 16%).  On the other hand, a dozen mostly rural counties lost population (Bear Lake; Butte; Caribou; Cassia; Clark; Clearwater; Custer; Elmore, Idaho, Lewis, Minidoka and Shoshone).  The remaining counties grew at very slow rates, well behind the 18% necessary to keep pace.

5. From a regional perspective, the northernmost counties (Benewah, Bonner, Boundary, Kootenai and Shoshone) currently contain 5 legislative districts, and that will almost certainly stay the same.  There will be some adjusting of lines within those 5 districts, as Kootenai has grown substantially (by almost 29,000 residents) while the other four counties grew at a much slower rate.  You can see the current map and district numbers here.

6. The north-central section, currently making up Districts 6 through 9, doesn’t fare so well.  Each of these districts grew at a much slower rate than the 18% necessary.  Four of the counties in these districts lost population.  None of the remaining counties grew very much. Currently, District 7 is about 2500 residents below the minimum necessary; Districts 6, 8 and 9 each are at least 5,000 below the minimum population for a district.  This region is going to shrink to three legislative districts and probably Valley or Payette counties will wind up in a district to the south.

7. Currently, district 11is comprised of Gem and part of Canyon counties, and districts 10, 12 and 13 are all within Canyon. But with the explosive growth in Canyon County major changes are likely.  Canyon is likely to gain a district, or at least most of a new district (perhaps shared with western Ada).

8. At present, Ada County contains 8 entire legislative districts (14 through 21).  But since the last census, the county population has grown by 80,000.  That means Ada is “due” another district (remember, the other 8 districts will absorb around 45,000 of the population growth).  

9. Districts 22-31 are all “light” on population from the ideal, although a few (especially Twin Falls) are within the permissible range.  This area, covering most of the Magic Valley, east-central and Southeast Idaho could lose a district.  

10. The remaining three districts (roughly, the Upper Snake River valley) will have to be reconfigured somewhat but will still contain three districts.

11. Finally, in the high growth urban counties of Ada, Canyon and Kootenai, unincorporated areas will lose strength as the suburbs have grown substantially.

Gary Moncrief
Professor of Political Science and a University Foundation Research Scholar at Boise State University