Congratulations, Minnesotans. Your state’s political districts probably aren’t unconstitutionally gerrymandered — at least according to a new equation that could become the gold standard for determining whether the shape of political districts unfairly favors one party.

In November, three federal judges ruled that Wisconsin’s state assembly districts were drawn in a way that unconstitutionally favored Republicans. The judges were convinced, in part, by calculations of Wisconsin’s efficiency gap, a simple equation that shows one party’s advantage over another in a district. Democrats in Michigan are planning to file a lawsuit on similar grounds.

The 2-1 Wisconsin ruling was a big deal for two reasons: first, because federal courts have never ruled that district lines have constituted gerrymandering based on party advantage (they have ruled on race-based gerrymandering cases), according to the New York Times. And second, because the courts have never used a mathematical determination for gerrymandering.

Now, the Wisconsin case is headed to the U.S. Supreme Court. If the high court affirms the lower court’s decision, the efficiency gap could be used far and wide, including in Minnesota, to shape statehouse and Congressional districts during the line-drawing battles to come in 2021. Some say that could be a game changer for Democrats, whose number of seats has eroded in recent years, both in Congress and in statehouses nationwide.

What is an efficiency gap?

The efficiency gap is the brainchild of researchers Nicholas Stephanopoulos and Eric McGhee, a professor at the University of Chicago Law School and a research fellow at the Public Policy Institute of California.

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To measure gerrymandering, the method relies on wasted votes. What’s a wasted vote, you ask? Not a vote for Jill Stein, at least in this case. Here, it’s any vote cast for the losing party’s candidate, or any vote cast for a winning candidate beyond the number of votes needed to win.

The whole point of gerrymandering, after all, is for the party in power to divide its voters into districts in a manner that allows them to win as many seats as possible. To do this, one has to either “crack” their opponents’ votes – breaking them up so they can’t win elections in a given district, or “stack” their opponents’ votes into a more limited number of districts the party in power can afford to lose. The nice thing about the efficiency gap equation is that it aggregates all the cracking and stacking in a state’s district map into one number.

To calculate the efficiency gap, you calculate all the wasted votes for each political party in all the races, find the net wasted votes, and then divide the net wasted votes by the total number of votes.

Researchers suggest anything above a 7 percent efficiency gap in a state legislative map in one party’s favor or the other’s is potentially unconstitutional. With a 7 percent or greater bias in one party’s favor, it’s statistically very unlikely the map will favor the other party, researchers have said. Wisconsin’s gap was 13 percent in favor of Republicans.

Minnesota’s efficiency gaps

Neither Minnesota’s state legislative district plans nor its Congressional District plan, set in 2011 following the last decennial Census, favor one party or another by more than 7 percent for statehouse maps or by the two seat threshold for Congressional districts set by the equation’s authors, according to MinnPost’s calculations of efficiency gaps using results from the November election.

MinnPost found that Republicans waste more votes across Minnesota’s Congressional Districts than Democrats, giving Democrats a 7 percent efficiency gap in their favor. Stephanopoulos and McGhee argue that efficiency gaps equal to two congressional seats are unconstitutional; with eight House total House seats in Minnesota, the efficiency gap would have to be 25% or more to be of concern. Five out of eight Congressional seats are currently held by Democrats.

The table below gives shows how we calculated the efficiency gap for Minnesota’s Congressional districts.

District Votes for R Votes for D D wasted votes R wasted votes Net wasted votes Total votes 1 166,526 169,074 1,273 166,526 -165,253 335,600 2 173,970 167,315 167,315 3,327 163,988 341,285 3 223,077 169,243 169,243 26,916 142,327 392,320 4 121,032 203,299 41,133 121,032 -79,899 324,331 5 80,660 249,964 84,651 80,660 3,991 330,624 6 235,380 123,008 123,008 56,185 66,823 358,388 7 156,952 173,589 8,318 156,952 -148,634 330,541 8 177,089 179,098 1,004 177,089 -176,085 356,187 Total: -192,742 2,769,276 Efficiency gap: -7%

The net wasted votes, which is negative because we subtracted Republican wasted votes from Democrats’, is divided by the total votes for an efficiency gap of -0.07, or 7 percent, in Democrats’ favor.

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Repeating this process for Minnesota’s 134 House Districts, Democrats waste more votes than Republicans. The Republican advantage here is a 7 percent efficiency gap — just at the 7 percent threshold, but not over it. Republicans currently hold the House majority 77-57.

In the Minnesota Senate’s 67 districts, Republicans have a tiny advantage, in the form of a 1.2 percent efficiency gap in their favor. Republicans took control of the Senate in November and now hold it 34-33.

These relatively fair results might be a reflection of the way Minnesota’s current district lines were drawn. Rather than being determined by politicians, in 2011 a lawsuit forced redistricting into court, and ultimately, a five-judge panel ended up setting the boundaries.

In an analysis of the 2012 elections, the Campaign Legal Center found gaps greater than 7 percent in 15 state legislature maps (Minnesota’s not among them), the Washington Post reported. Of the 15, 13 favored Republicans and two favored Democrats, leading some to believe that if efficiency gaps become the standard metric for gerrymandering, Democrats’ electoral fortunes could improve greatly after 2021.

Correction: This story has been updated to fix an error in the calculations of efficiency gaps.