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Population and Voter Registration Changes in Pennsylvania Since 2000

Using recently released U.S. Census data, we examine how changes in Pennsylvania's rural and urban populations relate to changes in voting habits.

Berwood A Yost
5 min read

Dear Readers,

This month’s newsletter discusses recently released Census data and how the widely reported changes in the state’s rural and urban populations relate to changes in the state’s voting habits. One of the most interesting findings about the state’s population changes, from a political standpoint, is that the state’s voter registration rolls have not changed in the same ways as its population.

Please keep an eye out for a special edition of our newsletter on October 28th that discusses the findings from our October 2021 Franklin & Marshall College Poll, which includes another look at the 2022 US Senate Primary races, voters’ feelings about an election audit, and support for a mask mandate in public schools.

Finally, I’d like to let everyone know that F&M Professor of Government Stephen Medvic is now the director of the College’s Center for Politics and Public Affairs. Medvic, who replaces the now retired Terry Madonna, teaches and writes on the role of political parties, the factors influencing campaigns and elections, and the public’s attitudes toward democracy. He is the author or editor of six books, most recently, Gerrymandering: The Politics of Redistricting in the United States. We are looking forward to working closely with Stephen.

Thank you for reading,

Berwood Yost

The US Census Bureau released 2020 Census data in August that showed the state's population grew modestly, about 2.4 percent, between 2010 and 2020.[i] Other top-line findings were that the state became a bit more diverse, with 75% of the population identifying as "white alone," and that a sizable number of the state's counties, particularly those in rural areas, lost population.[ii] In fact, many stories about the Census data focused on county-level change, the loss of population in rural areas, and how that might impact state politics, including redistricting.

We've been watching changes to the state's population and politics for years, particularly the stresses faced by our rural counties and the growing disparities in economic and population growth that are related to proximity to dense urban metro areas. The latest Census data allows us to look more closely at these changes and their political implications.

State Level Population and Voter Registration Change Since 2000

The state's population has grown 2.4 percent since 2010 and about 5.9 percent since 2000. Comparatively, the US as a whole has seen 7.4 percent growth since 2010 and 17.8 percent growth since 2000. But population growth is uneven across the state. Table 1 shows that the largest population growth has been in the state's medium metro areas, places like Berks, Cumberland, Dauphin, Lehigh, Northampton, and York counties, and that the population within the state's micropolitan and non core areas, the two most rural county classifications, has shrunk.[iii]

What is most interesting about these changes, from a political standpoint, is that the state's voter registration rolls have not changed in the same ways as its population. The state's two most rural county types, despite losing population, have not lost as much ground politically. Despite a population decline of 5.4 percent, voter registration has only declined 2.3 percent in micropolitan areas and has actually increased by 1.5 percent in non core counties, despite a population loss of about 4.5 percent. At the same time, the most urban counties, despite a modest population increase of 2.0 percent, has seen a decline of 5.0 percent in registered voters.

These registration changes make it clear how the state's political geography has readjusted itself in the past two decades. The most urban counties have lost some of their political punch while the large fringe metros that surround them have grown consistent with their population at the same time that they have tilted toward Democrats. The three most rural county types have increased their political punch relative to their population growth and have moved overwhelmingly toward the Republican Party.

The partisan shifts in the most urban and most rural counties have produced even more severe disadvantages for the out-party in those areas, while the partisan balance has tightened within the fringe and medium metros, which are undoubtedly the state’s true battlegrounds. Table 2 shows how the voter registration changes in Pennsylvania since 2000 have shifted the share of registered voters in each party in each group of counties.


The political implications of these population and registration changes are clear when the county-level results of the 2000 and 2020 presidential elections are compared. Figure 1 provides a direct comparison of Biden and Gore vote share by county, accounting for both urban-rural classification and geographic location. County names are shown in Figure 1 for those counties where the Democratic vote share declined by 15 percentage points between 2000 and 2020. Viewing Joe Biden's county vote share in relation to Al Gore's county vote share confirms the Democrat's sizable loss of support in virtually every one of the smallest counties in the state. This figure also shows that the state's primary battlegrounds are in the fringe and medium metros where Republicans hold the advantage in western Pennsylvania, while Democrats have made gains in the southeast and central counties.

Changes in population and voter registration over the past 20 years have made Pennsylvania's statewide elections remarkably competitive. If the patterns we've seen continue, the smaller rural counties will continue to be overwhelmingly Republican in their preferences and the residents of the large central metros of Philadelphia and Pittsburgh will strongly side with Democrats. This suggests the next decade will be largely decided by the voters in the large fringe and medium metros, where neither party has a significant registration advantage.

The partisan preferences that have emerged over the past two decades are aligned with the ideological viewpoints of the people who reside within these communities, as one might suspect. Figure 2 shows the mean operational ideological preferences of residents in each of these county classifications, with higher scores representing more conservative preferences. The key for both parties in Pennsylvania, at least for the next few election cycles, will be to craft messages that can appeal to the ideological dispositions of voters in the large fringe and medium metros without suppressing the turnout of the more ideological partisans within their strongholds.

References & Resources

[i] Redistricting Data Program

[i] Redistricting Data Program

Public Law 94-171 requires the Census to provide state legislatures with the small area census population tabulations necessary for legislative redistricting.

[ii] PENNSYLVANIA: 2020 Census

[ii] PENNSYLVANIA: 2020 Census

Surpassing Illinois as the fifth-largest state last decade, the Keystone State’s population climbed to 13,002,700 in 2020.

[iii] Franklin & Marshall - Pennsylvania NCHS Urban-Rural County Classification

[iii] Franklin & Marshall - Pennsylvania NCHS Urban-Rural County Classification

To conduct these analyses, we use a county-classification strategy that groups counties into six categories ranging from most urban to most rural.

Party Identity and PartisanshipPolitical GeographyElectoral ContextVoter RegistrationVoter Behavior

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