Is Population Density the Key to Understanding Voting Behavior?

On election night in 2012, I was at NPR headquarters in Washington, D.C. as part of a group of guest social media contributors and bloggers.

Listening to the election results come in, county by county, a pattern became clear: rural areas were going overwhelmingly for Romney, while cities were going for Obama. This was perhaps unsurprising — everyone expected Obama to do well in our major urban centers.

But the next day, I got to thinking about this pattern and set about pulling together the data. I wondered — is there a correlation between population density and voting behavior?

I began with analyzing the election results from the least and most dense counties and county equivalents. 98% of the 50 most dense counties voted Obama. 98% of the 50 least dense counties voted for Romney.

This could not be a coincidence. Furthermore, if the most dense places voted overwhelmingly for Obama, and the least dense places voted overwhelmingly for Romney, then there must be a crossover point: a population density above which Americans would switch from voting Republican to voting Democratic.

So I normalized and graphed the data, and there is a clear crossover point.

At about 800 people per square mile, people switch from voting primarily Republican to voting primarily Democratic. Put another way, below 800 people per square mile, there is a 66% chance that you voted Republican. Above 800 people per square mile, there is a 66% chance that you voted Democrat. A 66% preference is a clear, dominant majority.

So are progressive political attitudes a function of population density? And does the trend hold true in both red and blue states?

Red States and Blue States

Separating the results from states that went, as a whole, either red or blue, we can see that on a local level voting behavior is still directly correlated to population density.

Studying this graph, we see that first, there are very few cities in red states. Second, the few dense cities that do exist in red states voted overwhelmingly democratic.

Atlanta, New Orleans, St. Louis, Dallas, and Indianapolis are all in red states — and they all voted blue. And there are no really dense “cities” in red states that voted red. The only cities in red states that didn’t vote blue were Salt Lake City and Oklahoma City. And by global standards, they are not really cities — each has population density (about 1,000/sq. mi.) less than suburban Maryland (about 1,500/sq. mi.).

Red states simply run out of population at about 2,000 people per square mile. St. Louis is the only city that exceeds that density in a red state. It voted overwhelmingly Democratic (82.7%). In contrast, blue states contain all of the country’s biggest and densest cities: Washington D.C., New York City, San Francisco, Baltimore, Milwaukee, Philadelphia, Boston, etc.

Red States Are Just Underdeveloped Blue States

Historically, one can argue that red states have disproportionately affected election results by delivering a material number of electoral votes — and this is part of our constitutional design. But as cities continue to grow in red states, those cities will become more blue, and ultimately, those states will become more purple, and then blue.

If you follow the red state trend lines, you can clearly see that any dense, fast-growing cities that emerge in red states will be very likely to vote blue. The few that do already exist already vote blue.

Red state voters generally prefer low-density housing, prefer to drive cars, and are sensitive to gas prices. Once population density gets to a certain level, behaviors switch: high-density housing is the norm, public transit becomes more common, and gas use (and price sensitivity) drops. Red state values are incompatible with density.

Republicans: Fighting the Future

In the 1960’s, the Republican Party adopted the Southern Strategy as a way of moving white voters in the South from the Democratic party. This was a devil’s bargain: by marrying the party with the social issues important to rural voters (along with dog-whistle racism), the party was able to aggregate a relatively large voting bloc and field successful candidates over the course of several decades.

But pandering to rural voters came at a price. The Republican party effectively ceded cities and the dense coastal metropolitan areas to the Democratic party. In turn, the Democrats increasingly focused on a platform that was compatible with urban attitudes, while Republicans continued to refine a message that would resonate primarily with rural areas.

In 2016, Donald Trump has fully exploited this vulnerability by aggressively pursuing rural voters at all costs, and indeed, that is where his support primarily rests. But it is altogether unclear whether that cobbled-together bloc is enough to deliver an electoral victory.

Perhaps the biggest question of all, though, is whether pandering to rural voters is a viable strategy for the future. Arguably, it is not.

Globally, cities are growing rapidly as people move from rural to urban areas in search of opportunity. By 2030 it is estimated that cities will grow by 590,000 square miles and add an additional 1.47 billion people.

Only subsidized suburban housing and low fuel prices are insulating the United States from this global trend, and even with these artificial bulwarks, there is no good reason to think that America’s future lies in low-density development.

Density is efficient. Density produces maximum economic output. An America that is not built fundamentally on density and efficiency is not competitive or sustainable by global standards. And a Republican party that requires America to grow inefficiently will become extinct.

New Platforms, for Both Parties

If the Republican party wants to build a viable future for itself (or if a new party wishes to rise in its place), a very good place to start would be to drop social issues adopted to appeal to rural voters and build a new platform that meaningfully addresses cities: repairing and building infrastructure, effective and tolerant immigration policy, financial accountability, and ending the failed war on drugs would be great places to start.

Likewise, the Democratic party would be wise to address economic insecurity being felt in rural areas. And not by pandering to gun owners and those afraid of bathroom bogey-people: come up with a plan for how rural America will manage a prosperous transition from an agricultural past to a mercantile, information-driven future. The fact that this change is happening anyway and without a plan is perhaps the biggest source of anxiety in these areas.

A party system attenuated around the divisions between rural and urban populations is destined to become untenable if the country (and planet) continues in an inexorable progression towards urbanism. Maybe it’s time to identify a new axis along which to organize our political differences — because our current geographically-polarized approach is clearly obsolete.


This article is a revision and expansion of an article I wrote in 2012, which was referenced in the New York Times, Washington Post, and other publications. For thoughts on the polarization of rural and urban voters, see A Networked Theory of Trump Support.

© 2012 and 2016 by David Troy. For permission to use the graphs presented here please contact me.

Data Source: US Census 2010 (population density by counties); Politico.com election 2012 results by County.