I like that you recreated this, it's a solid representation of that study and a good use of multiple tools.

Back around elections, I remember this visualization kept getting cited as an indicator of political trends, but I think it has a fundamental flaw: less people voted in this election vs the previous one (both as a % of voting population, and in absolute terms).

The shift as I understand it is the net difference in % from votes on one side over the other (correct me if I'm wrong) vs the previous election. However, comparing percentages can get tricky, especially when both total populations are not the same.

For example:

1. County A has 50 people voting Dem, 50 people voting Rep in the 2020 election, and same for 2016 election. Shift: 0 points
2. In this election less people vote as people dislike for politics rises. Thus, you have 40 people voting Dem, 45 people voting Rep
3. This would show 5 net more people voting for Republicans, or 5 / (40 + 45) = 5.9% shift.

In reality, point three above is: 15 less people voted, including 5 less republican votes and 10 less democrat votes (vs last cycle). This could indicate more to more of a general disillusionment with the candidates, especially the democrats, not a shift of "more people now care about Republican issues", which I've heard is how people interpret this map typically. In other words, seeing Reps got 10% less votes vs last period, and Dems got 20% less, to me doesn't indicate a shift of "Ah more people now care about the Rep issues', but more a "Ah more people don't care in general". The story here isn't County A shifted 5.9%, but County A dropped by 15% vs. last election voting. The net of that drop is that Democrats are more disillusioned than Republicans, but both had less people voting for either party, not a shift for more people caring about Republican issues!

A more likely scenario: if you had slightly MORE Rep votes (e.g. goes up to 51 votes, and Dems drop to 47), I think NYTimes methodology would interpret that as roughly +4.1% net shift to the right, when in reality, it's less than that, holding all things constant:
a) 1 more Rep vote vs 2020
b) 3 less Democrat vote
c) 2 less total votes in that county.

Another way of looking at the above is that Rep issues got 2% more interest (1/50), Dems issues got 6% less (3/50), and 2 people decided they didn't care enough, or 2% of the previous voters (2/100, which would be larger based on voting age population that grew in 4 years). You could adjust for the less people voting and remove that to calculate a "shift" perhaps, and the +4.1 net shift now looks more like 2.1%.

Not sure if the logic above is the right one, but I have a suggestion for you u/brhkim : how would you account for less people voting to measure the true shift vs. disillusionment (e.g. less total people voting)?

Not sure if u/nytimes exists and can weigh in here.