Measuring Political Effect in Store Chains
Erik Josephson is our resident Data Scientist, and has started to explore our library statistically, looking for interesting trends and conclusions. He will periodically document his exploits here - part for the sake of curiosity and part to inspire you to find new ways to explore AggData on your own. If you have any experiment ideas for Erik to try, please contact us with your suggestions.
With the recent election, one of the questions that I really wanted to answer was which stores were leaning most toward Obama and which were most towards Romney. Using the complete list of all zip codes for each store in aggdata.com, we can attach each store location to the county level election results. Then, by associating those numbers with each store location’s zip code, we get an aggregate of the percentage of people voting for Obama per store. By adding up the total number of Obama votes as a ratio of total votes, we get a number for Obama’s share of votes per store.
The test was run on 1,873 stores. I decided to count only stores that had more than 50 locations, since a store chain with just two store locations in the most liberal part of the country would make it technically the most liberal store chain. The problem is that this doesn’t mean much because there are so few stores, so I chose 50 arbitrarily, as a rough estimate of when political leanings may be more evident. This took the list total down to 1,372.
Here are the top and bottom ten for Obama’s average percentage:
# locations |
Obama Share |
|
Pay O Matic |
93 |
0.843419921 |
Duane Reade |
255 |
0.807170966 |
C-Town |
76 |
0.77647703 |
Petland Discounts |
58 |
0.771389402 |
My Sports Clubs |
94 |
0.743944189 |
Lucky Supermarket |
65 |
0.736208766 |
Maui Divers |
51 |
0.72848989 |
Golden Krust |
69 |
0.719103001 |
Cosi |
100 |
0.715237435 |
Equinox |
53 |
0.714656017 |
Our Coop |
164 |
0.327055924 |
Harps Food |
64 |
0.323809726 |
Taco Mayo |
80 |
0.319134954 |
Tennessee Farmers Co-op |
119 |
0.318369622 |
Chicken Express |
171 |
0.312795213 |
Brookshire's Grocery |
118 |
0.30615403 |
Arctic Circle |
71 |
0.29167007 |
Food City |
79 |
0.286288669 |
Brookshire Brothers |
77 |
0.270405201 |
United Supermarkets |
50 |
0.251019143 |
The problem is that what we could be seeing is just a measurement of how urban a store is, since there’s a clear correlation between population density and left leaning tendencies. To factor this out, we figure out the rough regression line between population per zip code and Obama share per zip code.
Using this formula, we calculate the residuals per store location to get a measure of how far above or below the expected Obama share, given the zip code population. Thus, the higher the residual, the more liberal the store is, independent of the urban bias. With these adjusted values, here are the top and bottom ten of that list again:
# locations |
Residuals |
|
Duane Reade |
255 |
0.269663448 |
Pay O Matic |
93 |
0.251994728 |
Cosi |
100 |
0.234228975 |
My Sports Clubs |
94 |
0.232823168 |
Maui Divers |
51 |
0.227038125 |
Au Bon Pain |
188 |
0.223941494 |
Petland Discounts |
58 |
0.215109522 |
Equinox |
53 |
0.213164318 |
C-Town |
76 |
0.207240477 |
Lucky Supermarket |
65 |
0.202645904 |
Game Xchange |
56 |
-0.150127975 |
Braum's |
318 |
-0.151770819 |
Taco Mayo |
80 |
-0.154025071 |
Brookshire's Grocery |
118 |
-0.162281208 |
Hastings |
134 |
-0.165103232 |
Chicken Express |
171 |
-0.181092875 |
Brookshire Brothers |
77 |
-0.185282514 |
Food City |
79 |
-0.187167318 |
Arctic Circle |
71 |
-0.214405916 |
United Supermarkets |
50 |
-0.234106637 |
This shows how some stores have high Obama percentages mainly because they are urban centered stores. Famsa, for example, had a high percentage (60.5%) of votes for Obama, but the residual was only slightly above what would be expected, given the urban population where Famsa stores are located. Thus, Famsa is more of an urban store than an Obama store.
From all of this, we can conclude that if you had to pick a store chain whose CEO most likely voted for Obama, try Duane Reade.