More than I bargained for

A few days ago, the NY Times had an article on the increasing association between the prosperity and voting patterns of counties.  It noted that in 1992, there was a small tendency for poorer counties to give more support to the Republicans, but that this tendency has become stronger, and that in 2016 "the Republican Party won almost twice the share of votes in the nation’s most destitute counties — home to the poorest 10 percent of Americans — than it won in the richest."  There is a mistake in that sentence--the poorest 10% of counties are not home to the poorest 10% of Americans (although of course they are home to some of them).  I point that out not just to be pedantic, but because it will play a role in this post.  

The article also discussed some examples--Montgomery County in Ohio and Macomb in Michigan.  It said that both had declined in relative income, and had moved towards the Republicans.  It also mentioned Gallatin County, Montana, which had gained and moved to the Democrats.  However, these examples don't shed much light on the issue.  If there is a relationship between county affluence and party support, then it follows that places that change their relative standing will tend to change their voting.  But in order to understand why the relation arose in the first place, you should look at poor places that shifted to the Republicans and rich places that shifted to the Democrats.  

I don't have data on voting at the county level going back to 1992, but I do have data for 2016, so I decided to look more deeply at the relationship between economic conditions and party support in that election.  My general though was that it might depend on the distribution as well as the average level of income.  I tried to download statistics on average household income by county from the Census, but found that I had the percentage in sixteen different income categories.  Since I had them, I regressed the Republican lead in 2016 (Republican share minus Democratic share) on the the percentages.  Based on those results, I made five groups:  less than $10,000 a year, 10-15,000, 15-45,000, 45-100,000, 100-150,000, and 150,000 and up.  I will call those "very poor," "poor," "lower," "middle," "upper middle," and "upper." The regression results:

Constant     1.1
v. poor       -3.8
poor           -0.9
lower           0      [reference]
middle       -0.4 
u. middle   -1.1
upper         -3.2

So the predicted performance of Republicans is best when more people have moderate (or moderately low) incomes, and worse when more people are well-off or poor.  That is, the Democratic vote increases not just general affluence, but also the degree of inequality.  

In order to try to understand the relationship, I identified some counties with extreme predicted values and small residuals.  Some pro-Democratic examples:

                                  Predicted lead                                Actual lead
Westchester, NY           -.29                                       -.32  (32%-64%)
Fairfield, CT                 -.27                                       -.20  (38%-58%)
Norfolk, MA                 -.22                                       -.28  (33%-61%)

Some pro-Republican examples:

Baxter, AR                      .55                                        .54 (75%-21%)
Mifflin, PA                      .54                                        .57 (77%-20%)
Wabash, IN                     .53                                         .51 (73%-21%)


On the Republican side,  I restricted it to counties with at least 10,000 households.  As it happens, I know something about all of the Democratic examples--affluent suburbs of large metropolitan areas.  I didn't know anything about the others, but between the data and Wikipedia a few things emerge:
1.  They are not "destitute":  they're places where a lot of people have moderate incomes, but few have incomes over $100,000.  
2.  They are rural or small town; none of them are within commuting distance of major cities.  
3.   It doesn't seem that any of them are or were particularly dependent on industry--they seem to have fairly diversified economies.  

I will say more in future posts, but that gives me enough to think about for now.