  A key promise of democratic voting is that, by accounting for all
constituents' preferences, it produces decisions that benefit the constituency
overall. It is alarming, then, that all deterministic voting rules have
unbounded distortion: all such rules - even under reasonable conditions - will
sometimes select outcomes that yield essentially no value for constituents. In
this paper, we show that this problem is mitigated by voters being
public-spirited: that is, when deciding how to rank alternatives, voters weigh
the common good in addition to their own interests. We first generalize the
standard voting model to capture this public-spirited voting behavior. In this
model, we show that public-spirited voting can substantially - and in some
senses, monotonically - reduce the distortion of several voting rules. Notably,
these results include the finding that if voters are at all public-spirited,
some voting rules have constant distortion in the number of alternatives.
Further, we demonstrate that these benefits are robust to adversarial
conditions likely to exist in practice. Taken together, our results suggest an
implementable approach to improving the welfare outcomes of elections:
democratic deliberation, an already-mainstream practice that is believed to
increase voters' public spirit.
