Real cases
A case · you decide
Packing and Cracking draw the same state
Packing & Cracking — a 17-year-old in civics, comparing two maps of the same votes
Orange has 50% of the votes in a state with five districts. On one map, Orange wins one district with 90% and loses the other four at about 40% each. Orange wins 1 of 5 seats.
Packing: Orange's voters are crowded into one district, where most of their votes are surplus.
Cracking: the rest are split so they lose narrowly in each of the other four.
What explains 50% of the votes becoming 1 of 5 seats?
The votes are the same. The lines decide what they are worth.
A case · you decide
The district and The efficiency gap measure a sweep
The efficiency gap & The district — a 16-year-old analysing a state where one party won every seat
Orange won all 5 districts with 55% of the vote, 55 to 45 in each 100-voter district.
A vote is wasted if it goes to a loser, or to a winner beyond the 51 needed. Orange wastes 4 in each district (20 in total); Violet wastes all 45 (225 in total).
The efficiency gap is (225 − 20) ÷ 500, which is 41%. Researchers treat gaps above about 7% as worth a closer look.
What does the efficiency gap tell you here?
A measure can show a problem clearly without telling you who caused it.
Where this idea comes from· Boston Gazette 1812 · Rucho 2019
The salamander, and the court
In 1812 Massachusetts redrew its state-senate districts so that one party would win more seats. One district was so twisted that a cartoon in the Boston Gazette drew it as a monster, half salamander. The governor was Elbridge Gerry, so the drawing was called the "Gerry-mander".
One thing to hold: A wasted vote: a vote in a district your side wins by far more than it needs, or loses anyway. Drawing lines to waste the other side’s votes is how a gerrymander works.
Why it matters: In Rucho v. Common Cause (2019) the US Supreme Court decided, 5 to 4, that federal courts cannot decide when drawing lines for party advantage goes too far. That leaves it to states, their courts and their voters.