Enigmas & puzzles

May 20, 2005
Proportional misrepresentation

It was election time in the Democratic Autocracy of Rigvotia, and the ruling Dictatorial-Democratic party was in trouble. An economic slump had forced Rigvotia to join the Subsidised Trade Alliance, whose member states insisted on the transferable ranking electoral system.

In this system, each voter ranked the political parties in order, and all subsequent decisions were based on those rankings. If any party was ranked first by more than 50 per cent of the voters, that party won. If not, two parties were chosen at random, and their rankings were compared across all voters. Whichever party lost was then eliminated, and the process continued with the remaining parties.

Rigvotia had three political parties. When the votes were counted, 49 per cent of the electorate preferred the Paternalists, 49 per cent preferred the Autocrats, and only 2 per cent preferred the DicDems.

"We've lost," said the president. "I shall declare a state of emergency—"

"Perhaps," mused his minister for graft, "that will not be necessary. Both of our opponents have less than 50 per cent of the vote, so there must be a run-off."

"Look at the figures, man! It's a disaster!"

"I have looked. The results are curious. The 2 per cent who rank us first all rank the Autocrats second. The 49 per cent who rank the Autocrats first all rank the Paternalists second. And the 49 per cent who rank the Paternalists first all rank us second."

"I don't see how that helps. I will order the secret democratic police—"

"There's no need. All you have to do is rig the choice of parties for the run-off."

Which two parties must take part in the run-off to ensure that the DicDems are elected?


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The answer

The run-off should pit the Autocrats against the Paternalists.

If the DicDems take part in the run-off, they will be eliminated by 98 per cent to 2 per cent whichever party opposes them. However, if the Autocrats are run off against the Paternalists, the Autocrats will win by 51 per cent to 49 per
cent. With the Paternalists eliminated, 51 per cent of the voters then prefer the DicDems to the Autocrats.

The winner is José Miguel Urbano from Coimbra, Portugal