Gauging the Level of Over Time Issue Polarization among Partisans

The question of the extent and nature of polarization in the American public has received much attention from political science. Though not always debated on this front, polarization on issue and policy opinion is a nuanced subject and sometimes suffers from limitations from survey data. For example, survey questions on policy issues often offer binary responses, which can measure what side individuals fall on but not the extremity of their positions. Furthermore, most data sources on mass issue opinion lack the ability to give a historical account of polarization, as they simply have not been asking questions long enough. The American National Election Studies does not suffer from these pitfalls as much, however, having asked many of the same issue and ideological questions across several decades and doing so with survey scales that capture position extremity. As a result, analyzing the ANES can produce a uniquely informative picture of over time polarization on issue/policy opinion–namely, speaking to how divided Democrats and Republicans have become in their opinion across various issue domains.

That’s what the below graph illustrates–the average position of both major partisan group for nine issue/ideological time series questions asked in each ANES survey over the past few decades. Some of these questions fall on four- or seven-point scales in their original form, so to make them comparable, I code each to run on a 0 to 1 scale where 0 marks the most liberal position on the question and 1 represents the most conservative position.


From a qualitative perspective, these average partisan positions on several issues suggest not much ideological polarization has developed over the last few decades. Partisan gaps certainly stay constant throughout the years on every issue and some issues do see growing differences (e.g. abortion rights opinion comes closest to movement to the ideological “poles”). But for the most part, Democrats and Republicans appear to (1) not be substantially divided on the issues and (2) their divisions do not appear to be growing too heavily. Instead, year-to-year changes in opinion across both partisan groups seemingly track one another, offering support for a “parallel updating” account. For example, over time correlation coefficients between each partisan group’s position are mostly positive (for seven of nine positions) and moderate to strong in size (0.10, 0.26, 0.29, 0.30, 0.48, 0.90, 0.91 for the seven).

On the other hand, plotting the yearly differences between Democrats and Republicans on each position from above makes it makes it clear that for most areas, partisans are moving further away from each other on the issues over time. The below graph depicts these gaps and corroborates this trend of growing divisions.


This graph puts a “magnifying glass” to the differences, so it’s worth keeping in mind the y-axis scale being used and how that accentuates these gaps. The growing differences are still not too sizable by any means–and not to the extent of considerable polarization in issue opinion that many often assume defines American politics. Nevertheless, divisions on the issues indeed have grown over the last few decades and up through the last election year, occurring most acutely for abortion rights, government aid to blacks, and self-described ideology.

Many might interpret these growing opinion divisions among the partisan masses as a response to growing polarization among party elites. In this sense, we might expect partisans who are most politically aware and attentive to elite discourse to receive elite cues about changing issue positions the most and change their opinion in ideologically consistent directions to a greater degree. The below graph plots the same average partisan position difference from above in green and the difference for only the most politically knowledgeable individuals in orange. Correct answers to a question about what party has a House majority–which, importantly, is a political knowledge question common to all the survey years of interest–distinguishes high knowledge respondents.


Comparing average partisan distance for all respondents versus just high knowledge ones confirms the expected pattern: high knowledge partisans–those likely most receptive to elite cues on policy issues–lead the way on driving ideological polarization. The orange line representing them for the most part lies above the green line (all people) across most years and issues, demonstrating greater issue opinion difference exists (which the y-axis measures) for this group. While there isn’t a good comparison for this dynamic, it is interesting that these differences between high knowledge and all individuals are not that large–absent for some issues and muted in others.

Gauging the Level of Over Time Issue Polarization among Partisans

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