This piece was written by Brielle Collins, Grace Hennessy, and Katie Parkins, students at Wellesley College, and Ismar Volić, a professor of mathematics at Wellesley College, the director of the Institute for Mathematics and Democracy, and the author of Making Democracy Count: How Mathematics Improves Voting, Electoral Maps, and Representation.

When the Wisconsin Supreme Court struck down the congressional and state district maps last December and ordered new, fairer ones to be drawn, the state had the opportunity to do away with a lesser-known form of district manipulation — prison gerrymandering.

Gerrymandering usually conjures images of wonky-shaped districts designed in a way that maximizes the number of wins for one party. This makes sense since gerrymandering is usually about employing demographic and voting data to creatively meander district borders through counties, towns, and neighborhoods in order to influence the count of the voters of one or the other party living in them.

The gerrymandering adage “the party chooses the voters, not the other way around” holds true because the goal of this practice is to make sure that certain voters live in certain districts. But when characterized this way, the reach of gerrymandering widens to include an especially problematic variant called prison gerrymandering – incarcerated people being counted as residents of the district that houses the prison instead of their pre-incarceration home address.

This practice is as old as the Census, which defines residence as the place where a person “lives and sleeps most of the time.” Since the first Census in 1790, the federal government has accordingly counted incarcerated people in the districts in which they are confined. While this probably did not seem like a big complication at the time, the current U.S. incarceration rate of 2.3 million, the largest in the world, has made it so. The essential irreconcilability is that, even if they are counted as residents, those who are imprisoned cannot vote (except in Maine and Vermont). If it reeks of the three-fifths compromise, it’s for good reason.

Inmate numbers do not typically make a big difference in congressional races, but they do at the state and local levels where the prison population might constitute a large portion of the residents. In 2008, seven New York state districts would not have even been districts if they hadn’t contained prisons (New York eliminated prison gerrymandering in 2010).

This skews representation and gives more voting power to the voting residents in those districts. In the city of Waupun, Wisconsin, 76% of the population in one district are incarcerated people. The number is 61% in another district where the representative was reelected in 2019 with 43 votes. To win in another district, many more votes would have been needed; hence the inflated voting power of a resident in a district containing the prison.

Voters in some Wisconsin districts containing prisons have as much as three times the voting power of their counterparts in other districts. An even more extreme example comes from Anamosa, Iowa, where 96% of the population of one of its city districts in 2008 consisted of people in prison. Of the 1,400 official residents, only about 100 were eligible to vote. Danny Young won a city council seat with just two write-in votes, one from his wife and one from his neighbor.

The implications of prison gerrymandering for racial inequality are also evident. The prison system disproportionately affects Black, immigrant, and low-income populations. Black people are imprisoned at four times the rate of white people, with 1 in 41 Black adults behind bars in state prisons as of 2020. The prison system relocates the inmate population away from urban communities and into white rural communities, effectively cracking them across districts where they have no voting power due to incarceration.

In the same city of Waupun, only about 4% of the non-incarcerated residents are Black while the prison housed there is 60% Black. In Maryland, 40% of incarcerated people are from Baltimore, a majority of them Black, but 90% have their official residence elsewhere. In Pennsylvania, a 2019 study found that about 100,000 Black men are underrepresented due to prison gerrymandering; if they were counted at their homes instead of the place of their incarceration, the city of Philadelphia would have gained one, possibly two majority-minority state house districts in 2011.

Most of those who are incarcerated are released within three years of their imprisonment, returning to their previous homes. But since the Census is decennial, they continue to be  counted with the population of the district where their former prison is located, perpetuating the lopsided representation long past the end of their sentence.

Wisconsin missed the chance to fix prison gerrymandering. Governor Tony Evers signed new legislative maps into law this February without addressing the problem. Nevertheless, sixteen states are doing something about it, including outright banning it and planning to record each prisoner’s pre-incarceration address in the 2030 census. Some have a system in place that modifies the appropriate census files to accurately reflect any inmate’s address as the pre-incarceration one.

But these state-by-state solutions are expensive and logistically taxing. The swiftest way to enact such a change nationally would be for the Census Bureau to change its residence rule and prohibit the use of an incarcerated person’s temporary address—the prison—in the census. In 2010, the Census Bureau cited “logistical and conceptual issues,” refusing to address the problem. This despite the glaring contradiction in its own mechanisms that, for example, count students in boarding school as residents of their homes and incarcerated kids as residents of the detention facilities.

The End Prison Gerrymandering Act, currently in Congress, would compel the Census Bureau to count an imprisoned person’s residence as their last home address. The future of the act is unclear. Because rural districts are predominantly Republican and the perception is that they benefit from inflated populations, Republicans are less keen on fixing the issue than Democrats.

But prison gerrymandering is not necessarily partisan. A new report by the Prison Policy Initiative, an advocacy group fighting prison gerrymandering, shows that, of the ten state districts with the highest percent of incarcerated population that is counted as residents, six are held by Democrats and four by Republicans. Based on this data, partisanship does not drive prison gerrymandering, but, as is the case with most issues in front of the Congress these days, politics have made it so. We must move past the perceived divisions and support the End Prison Gerrymandering Act, a popular and sensible legislation. It is not just a question of equity and representation, but also one of basic human decency.