Three kinds of polarization

I'll start by answering a question in a comment on my last post:  where can you get these data?  One way is to download the data from the American National Election Studies data center and then analyze them using a statistics program; the other is to analyze them online from the SDA (Survey Documentation and Analysis) site.  I use both, but usually SDA--it's faster for simple analyses.  

The ANES survey has thermometers for the parties, the presidential candidates, and liberals and conservatives.  A few years ago, I showed the correlation between ratings of the Democratic and Republican parties.  Here's the figure updated to include 2020:

There was a substantial drop between 2000 and 2004, and no consistent change since then.  That's kind of surprising, since the general perception is that polarization has increased substantially in the last 10-15 years.  

From 1964 to 1982, the ANES asked about ratings of Democrats and Republicans.  The correlations:

The first time it was asked was after the Johnson-Goldwater race, when there was large ideological gap between the parties.  But even if you leave that aside, polarization declined (since a negative correlation indicates polarization, an upward slope is a decline in polarization) from the 1960s to the 1970s.  

There are also thermometers for the presidential candidates starting in 1972:

In contrast to the questions on the parties, this shows a substantial recent increase in polarization.  The correlation between ratings of Trump and Biden in 2020 was -.787, which is remarkably high for individual-level data (the correlation between ratings of the parties in 2020 was -.48).  

Questions on liberals and conservative in 1964:

There isn't much trend through 2008, then a big increase in polarization in 2012, with smaller increases in 2016 and 2020. 

What I find most striking in these figures is that polarization was probably lower, and certainly not higher, in 2016 than in 2012.  The substantial increase between 2000 and 2004 is also noteworthy.