What percent of counties that voted Democratic in 2016 are minority majority?

Question

I stumbled across an image at https://ibb.co/GF5zPc4 that shows minority majority or majority minority counties as brown and the ones that almost had minority majority status as yellow. It also shows the 2016 electoral map for President of the United States. I noticed that most of the counties that voted blue were highlighted as majority minority except for mainly the New England area. This is not for commentary. What percent of the counties carried by Clinton have a non-Hispanic White population less than 50%?

Note: this does not work at the state level so much (3/4 states like this vote blue but there are many more blue states), but it does seem to correlate strongly at the county level.

Answer 1

I have no idea what use this information is, but I was interested in whether I could find the data to answer it, so I gave it a shot.

Using the vote data from this dataset about the 2016 election and this list of counties with majority minority populations (from 2018), I wrote a bit of code to compare and report.

Based on my numbers, of which I've done very little proofing, 160 out of 3152 county-like areas (5.1%) have majority minorities. Of that, 116 voted for Clinton (3.7% of the total, or 72.5% of the MM counties).

Filtering out majority-Hispanic districts, there are 91 MM counties (2.9%), of which 83 voted for Clinton (2.6% of the total, or 91.2% of the remaining MM counties).

To address the question in the title, my numbers show 503 counties that voted for Clinton, so 31.8% or 16.5% of counties that voted for her are majority minority (depending on whether you count majority-Hispanic ones).

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All this really says, though, is that African Americans voted overwhelmingly for Clinton, as shown in the first graph on this page, and thus in areas where they are more concentrated, her vote share was high.

Answer 2

In addition to Bobson's answer and comment, I ran the numbers using the data which Brian Z linked to in his comments. I have used the estimated population data for 2016, and the county-level results from here.

I found that of the 3142 counties in the population dataset, 177 had a majority-minority population, which I defined as (white_male_pop + white_female_pop) < total_pop/2. In this data set, 'white' does not include Hispanic Americans.

Of the 3118 counties in the county result level dataset, 497 are recorded as voting for Clinton.

Of these 497 counties, 142 had a majority-minority population, so to answer the question in the title, this data shows that 28.6% of counties voting Democrat in 2016 were majority-minority.

The differences between my answer and Bobson's are due to two factors. Firstly, the differing definitions of 'county' between the datasets - this is not as clear cut as you might think, for example Time magazine reports that Clinton won 503 counties to Trumps' 2649, a total of 3152, however AP reports that Hilary won 487 counties to Trump's 2626, with a total of 3113 counties. Secondly, Bobson has used the population estimates for 2018, and I have used the population estimates for 2016.

Hopefully, however, the combination of the answers is good enough to give you a fairly accurate picture - somewhere around 30%.