What’s the difference between an “undocumented worker” and an “illegal alien”? If this sounds like the setup for a groan-worthy political joke, it is—in a sense. The unfortunate punch line? It depends on whether you’re a Democrat or a Republican.

Democrats and Republicans live in different worlds in the United States—assuming different political attitudes, preferences, and fundamental beliefs—and yes, using different vocabularies. Politicians may have helped exacerbate the tension between political parties by using increasingly polarizing language over the years.

Recommended Reading

Measuring polarization and behavioral differences among groups is a perennial challenge for social scientists because of the many random variables to consider. To broach the subject of political polarization, Stanford’s Matthew Gentzkow, Jesse M. Shapiro of Brown University, and Chicago Booth’s Matt Taddy home in on one variable—language. Their research relies on a model-based measure that breaks down and analyzes the differences in rhetorical choices among US political party members, following the trends over a long period of time.

A line chart plotting the use of four race-related phrases, with a y-axis ranging from two, for something more likely to be said by a Republican to negative two for something more likely to be said by a Democrat, and the years of 1873 to 2009 on the x-axis. A line tracking the phrase civil rights stays at zero over the whole time span. A line tracking the phrase colored people rises to nearly two and remains in the Republican half of the graph until about 1930 when it crosses over and remains in the Democratic portion, reaching negative one in about 1990. A line for illegal immigrant stays at zero until about 1980, when it begins shifting to one in the Republican half. And a line for African American stays at zero until the late nineteen-sixties, when it sharply shifts into the Democratic half to nearly negative two-point-five. A second line chart plots the use of four tax-related phrases in the same way. First, the phrase raise taxes stays at zero the whole time. Second, the phrase death tax stays at zero until the late nineteen-nineties, when it begins a shift toward one in the Republican half. Third, the phrase estate tax fluctuates between zero and slightly into the Democratic half until the nineteen seventies when it crosses well into the Republican half until about 2000. And fourth, the phrase tax break stays at zero until the mid-nineteen-sixties, when it crosses over to the Democratic half, reach about negative-one-point-five by the nineties.

In tackling an extended timeline, the researchers faced yet another challenge: the standard measures of difference and segregation are constantly shifting over time. Gentzkow, Shapiro, and Taddy developed a new approach, focusing specifically on congressional speech and characterizing particular phrases according to their partisanship.

To develop their model, they used an automated script that sorted the text from the United States Congressional Record from the 43rd to the 110th congresses (spanning 1873 to 2009) into individual speeches. They also matched the speaker of each line of text to a particular congressperson using the Database of Congressional Historical Statistics.

Using a “bag of words” approach, which disregards grammar and word order and focuses instead on counting the frequency of “bigrams” or two-word phrases appearing across speeches, the researchers came up with a sample of 723,198 unique phrases spoken a total of 271 million times by 7,285 unique speakers, creating a large volume of data on different speakers’ tendencies to “talk like” a Republican or Democrat.

The findings indicate a distinct shift in language over time. For example, a phrase like “tax break” did not become partisan until the late 20th century, the researchers say. In addition, their research suggests that the language used across party lines has become increasingly polarized, particularly from the 1980s onward.

And indeed, examples of polarizing language are littered across congressional speech, and will sound familiar. What Democrats call “estate taxes,” for example, Republicans refer to as “death taxes.” The “undocumented worker” of Democratic lexicon becomes an “illegal alien” in Republican terms. And what Republicans refer to as “tax reform” is dubbed by Democrats as “tax breaks for the rich.”

“These differences may contribute to cross-party animus, and ultimately to gridlock and dysfunction in the political system,” the researchers write.

Gentzkow, Shapiro, and Taddy suggest that looking more closely at the effects of such polarizing language could help us better understand the root cause of problems within our political system.

More from Chicago Booth Review

More from Chicago Booth

Your Privacy
We want to demonstrate our commitment to your privacy. Please review Chicago Booth's privacy notice, which provides information explaining how and why we collect particular information when you visit our website.