Real cases

Two of the ideas you practise, meeting in one real situation. Choose, see what actually happens, then reflect.

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

The idea in play: packing puts one side's voters into a few landslide districts; cracking spreads the rest so they fall short everywhere else.

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?

Draw the districts →

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

The idea in play: winner-take-all wastes votes, and the efficiency gap measures whether one side wastes far more — a flag, not proof of intent.

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?

Draw the districts →