Recently, I was on a trip with my
family, and we listened to an NPR podcast called “Who’s Gerry, and Why is he so
Bad at Drawing Maps?” The issue that was
being discussed is a case (Gill v. Whitford) that the supreme court was about
to hear at the time. In 2010, many state
legislatures around the country were controlled by republicans. Also in 2010, there was a census. This means that all of these republican
controlled legislatures would be redrawing electoral maps for their
states. Naturally, the republicans drew
up maps that would benefit themselves.
This particular case is from the
state of Wisconsin. In 2012, democrats
got 53% of the votes, but only 39% of the seats. The republicans managed this by packing
democrats into districts where their votes would be, essentially, wasted, and
dividing up remaining democrats into areas dominated by republicans. This case was prominent because it was taking
place right before the lines being redrawn again in 2020.
One of the biggest problems with
drawing electoral districts is that it is not as simple as it seems. In a perfect world, each district on the map
would have the exact same population and a 50/50 split of republican and
democrat. Obviously, this cannot be
achieved by simply drawing some rectangles on a city. Real electoral maps, generally, look funny
because the districts are all kinds of abstract shapes and sizes.
A few years ago, the supreme court
heard a different case about gerrymandering of electoral maps. Basically, the justices decided to ask the
public what to do about it. Justice
Kennedy basically issued a public challenge to see if anyone could come up with
a solid solution to this problem. As it
turns out, the answer can be found through math. Two political scientists developed an idea
called the “efficiency gap formula.”
This formula is a simple math formula that allows anyone with access to
the proper statistics to be able to take out a calculator and quickly see how
fair the electoral map is. The
efficiency gap formula does this by measuring the amount of “wasted votes.”
Here’s how it works: First, the number of wasted votes is
counted. Any vote that does not
contribute to the victory in the election is considered a wasted vote. Votes that go over the simple majority needed
are also considered wasted votes (if there are 100 voters, any vote over number
51, for the winning candidate, is a wasted vote). Any vote that is for the loser of the
election is also “wasted.” The
efficiency gap is the difference between the number of wasted votes on each
side divided by the total number of votes.
In the end, you get out a percentage that shows which party is
benefiting most from the current legislative districts. In short:
After the numbers are plugged in, the
efficiency gap will be a percentage.
Researchers say that a gap greater than is too extreme
of a gap. A gap between 0% and 7% is a
fair map. A gap greater than 7% is
Below is an example of the
efficiency gap at work. There is an area
with 20 A voters and 30 B voters. The
area is divided into five electoral districts with ten people in each one.
There are two groups
with nine B’s and only one A. The other
three groups have six A’s and four B’s.
In the next visual, the areas with majority A are highlighted with pink,
and the areas with majority B are highlighted with yellow.
As shown by the drawing,
we can see that even though the B’s are majority in the population, it will be
extremely difficult for them to win the majority of the seats in the
legislature. The A’s will most likely
win seats in the pink districts, and the B’s will most likely win in the yellow
districts. Just from this example, we
can see that this map is gerrymandered to favor the A voters, but we can prove
it with the efficiency gap. The “wasted votes” are marked out with x’s in the
Party A wasted
Party B wasted
() 100 = 32%
The efficiency gap is
32%, which means the map in this area is extremely unfair for party B.
gap can also be used to calculate the number of seats that should be won based
on the percent of the votes received.
First, you take the percent of the votes received, 57% for example. Then calculate what percent of the votes are
wasted. In this case it is 7%. Next, double this percentage (14%). Finally, add this percentage back onto the
original percentage of the votes. With
this formula, if a party gets 57% of the votes, then it should have 64% of the
seats in the legislature.
(Percentage of votes) + (percent of wasted votes )
concept was created based on actual elections.
This doubling of the margin is what actually tends to occur in real
life. This idea is called a “seat
bonus.” The party with the majority of
the votes gets a small percentage bonus in seats in the legislature.
efficiency gap is a concept created in response to a supreme court case that
deals with gerrymandering of electoral maps.
Basically, the efficiency gap formula gives the judges, as well as the
public, a way to mathematically prove that an electoral map is fair or unfair
for a political party. Now, anyone with
the proper information can easily plug in numbers and figure out a simple
percentage that tells whether or not an area is fair. Concepts from the efficiency gap formula can
also be used to determine what percent of seats a party should hold in
legislature based on the amount of votes that party received. With the next census coming up in 2020, the
emergence of the efficiency gap in 2017 could play a major role in elections
from 2021-2030. After the maps are
redrawn and one election passes, the government will have the ability to easily
check every map, and they will have a reason to make changes to unfair maps.
“Here’s how the Supreme Court could decide whether your
vote will count.” The Washington Post,
“Who’s Gerry and Why Is He So Bad at Drawing Maps?” WNYC,