[SBU Board] Geographic demographics of U446 membership vs.population as a whole

[LARRY HOLDREN]

Very interesting, Mike, and it looks like a good bit of work. 

These data seem to say that we don’t need to give much consideration to “south” folk participation.  I don’t know how members there are in Pierce County, but we did not get many to Kent.

Larry

From: Michael J Ring 
Sent: Sunday, September 25, 2016 12:12 PM
To: Seattle ACBL Unit Board 
Subject: [SBU Board] Geographic demographics of U446 membership vs.population as a whole

All,

I had a chance to run the unit membership by geographic subdivisions of the county as Tim suggested earlier in the week. If you are interested I've tried to describe a bit more about my methodology below, and if you're really interested I'd be happy to answer additional questions about what I did and why. Otherwise feel free to skip down to the table below.

Methodology:

I used ZIP codes/Zip Code Tabulation Areas to determine the population of Unit 446 members by location, versus the general population as a whole. ZIP codes are preferable to use as compared to city names, as zip codes and city boundaries do not necessarily align well. This is especially true in King County, where many cities were incorporated in the 1990s, long after ZIP codes came into use. Also, default place names do not necessarily correspond to place names commonly used for an area. For example, any zip code of the form "981xx" is assigned the default place name "Seattle, WA" by the USPS, even though this area stretches as far north as Shoreline and as far south as Des Moines. Some members in those ZIP codes have their actual cities listed as their address, but a few have the default "Seattle, WA" as their address even though they do not live within Seattle city limits. By using ZIP codes this problem is eliminated.

The ZIP codes in our service area are all 980xx and 981xx zip codes EXCEPT 98020, 98026, 98036, 98037, 98043, and 98087 (which are in the Everett unit) and 98110 (which is in the Tacoma/Kitsap unit). We also appear to have in our territory 98224 and 98288 (which are Baring and Skykomish, but have only 1 ACBL member between the two of them).

I assigned each zip code into one of several geographical areas as follows. The main places in each of these categories are as follows:

Central Seattle - the area between the south Seattle city limit and Northgate
North - Seattle north of Northgate, and Shoreline/LFP/Kenmore/Bothell/Woodinville
East - Kirkland, Redmond, Bellevue, the small towns between Bellevue and the lake, Sammamish, Issaquah, Mercer Isalnd
Valley - Everything east of Issaquah + Duvall/Carnation
Near South - Renton, Seatac, Tukwila, Burien, Des Moines
Far South - Federal Way, Kent, Auburn, Covington, Black Diamond
Island - Vashon 

I then counted the number of members in each zip code (excluding members who did not report the address to our database and members keeping a primary address outside the unit), tabulated up the results for each geographic category, and did the same for the population at large.

Results:

Our membership statistics are in the yellow cells, and the population at large in the red cells.
  Population by Geographic Region of U446 Service Area 
      Region Unit 446 Percent Total Population Percent 
      Central 399 28.89% 532594 26.12% 
      North 159 11.51% 316773 15.54% 
      East 582 42.14% 405917 19.91% 
      Valley 15 1.09% 50261 2.46% 
      Near South 92 6.66% 313161 15.36% 
      Far South 88 6.37% 409703 20.09% 
      Island 46 3.33% 10624 0.52% 
      Total 1381 
     2039033 
     


Compared to the general population of our service area our members are heavily skewed toward the Eastside, with over double the percentage of members living there as compared to the population as a whole. In contrast the south end is underrepresented in our membership compared to the population as a whole - less than half of the percentage expected from the population as a whole.

I'd be happy to tease more specific data out or try some different divisions for any Board member who is interested - just let me know.   


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