[EM] Markus & Manipulability

[Forest Simmons]

On Mon, 4 Feb 2002, Forest Simmons wrote:

> My thinking about Nurmi and Bartholdi's measure of manipulability is
> similar to Mike's.
> 
> Consider the example of Perverse Random Ballot: the winner is the
> candidate at the bottom of the list on a randomly chosen ballot.
> 
> The optimum strategy is completely obvious: vote your favorite last.
> 
> [As a side note, this is like the shower valve that has "hot" and "cold"
> reversed. Richard's point about isotone versus monotone applies.]
> 
> According to Nurmi and Bartholdi this method is highly manipulable because
> the voter can easily subvert the system to increase his expected utility
> by voting strategically.
> 
> But notice that under Perverse Random Ballot the voter cannot be easily
> manipulated into voting against his own best interest.
> 
> Manipulating a voter into voting against his/her own best interest is the
> anti-democratic kind of manipulation.  Nurmi and Bartholdi's levels do
> not address this most important kind of manipulation.
> 
> This example shows clearly that Nurmi and Bartholdi are worried about
> voters "manipulating" the system to increase their expected utilities,
> i.e. to vote in their own best interest, as though voters' utilities had
> nothing to do with social utility.
> 
> It is the prerogative of the voter to maximize their own utilities,
> whether anybody else thinks they have social value or not. That's
> democracy. We don't try to use voting methods to protect the public
> against the public will. We use voting methods to ascertain the public
> will. 
> 
> A more realistic worry is pollsters and pundits manipulating the voters by
> fooling them into voting against their own best interest. The more
> complicated the strategy and the more sensitive good strategy is to
> information (like the other shower valve with hysteresis near its hot/cold
> boundary) the easier the "experts" can manipulate the vote of the
> gullible voter.
> 
> 
> Forest
> 

One more comment relative to this last paragraph.  Markus asked the
question about defense versus offense.  In the context of this last
paragraph we could ask, how can the pollsters and pundits fool the voters
into voting in a way that favors (for example) corporate utilities, when
the voters' strategy for self interest is (for example) intractable
(Nurmi's level V)?

Two replies:

(1) Strategy for corporate interest might be relatively simple compared to
strategy for civic utilities. Consider the shower analogy again.  If the
experts want to scald you they don't have to know a strategy for finding
that elusive warm setting that you think would be most beneficial. The
more elusive that setting, the easier for them to scald you at least half
of the time.

(2) The experts have resources for calculating strategies that ordinary
citizens do not have, so they are in more of a position to fool the
gullible when the strategy is complicated than when it is simple.


Forest