Democratic Demagoguery

Logic; Difficulty: easy

Jack Sparrow
PC: magicalquote.com

Can a leader get people to vote to make him(her)self richer?

Puzzle worm Sandi Sandman sent me this simple yet interesting puzzle. Interesting because it offers a model, even if overly simplistic, of how a self serving politician in a seemingly democratic set up can end up impoverishing others while enriching themselves. 

Jack Sparrow and his crew of 129 pirates have 1 gold coin each (130 coins in total). As captain, Sparrow can propose changes to matters on his ship including coin redistribution. But as a democratic bunch, they always vote on proposals. However, votes for Sparrow’s proposals are only cast by the 129 pirates; Sparrow himself never gets to vote as he is the one always making the proposals.
A pirate votes in favor of a Sparrow proposal if he gains by it (with certainty), and votes against it if he loses due to it (again with certainty). If a pirate will neither gain nor lose with a proposal, he abstains from voting. If there are more votes in favor of a proposal than against it, then the proposal is accepted by everyone, otherwise it is rejected.

Question: Can Sparrow end up with more than the single gold coin he started with, and if yes, what’s the maximum number of coins he can appropriate? Note – a coin cannot be broken up into fractions.

*spoiler alert*  solution and answer follow in the expandable sections below.

Proposal 1: Jack first proposes that he and 64 other chosen pirates give up their coins to the other 65. This readily passes because the 65 pirates who stand to double their spoils all immediately vote Aye.

Proposal 2: Jack next proposes a coin redistribution such that 32 of the remaining 65 give up their coins so that the remaining 33 end up with one additional coin (3 in all) and Jack with 31 coins. This too, obviously passes.

Jack continues to whittle away coin holders in this fashion such that seven such proposals later we are left with 2 pirates each having 8 coins and the remaining 122 coins held by Jack himself!

At this point, Jack makes his final masterstroke proposal: to re-distribute from the current two coin holders, one coin each to 3 currently pauper pirates and the rest of the coins to himself, thereby appropriating 127 coins for himself!

This is the best Jack can do and the quickest way to get to the maximum. 

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