  Strategic voting, or manipulation, is the process by which a voter
misrepresents his preferences in an attempt to elect an outcome that he
considers preferable to the outcome under sincere voting. It is generally
agreed that manipulation is a negative feature of elections, and much effort
has been spent on gauging the vulnerability of voting rules to manipulation.
However, the question of why manipulation is actually bad is less commonly
asked. One way to measure the effect of manipulation on an outcome is by
comparing a numeric measure of social welfare under sincere behaviour to that
in the presence of a manipulator. In this paper we conduct numeric experiments
to assess the effects of manipulation on social welfare under scoring rules. We
find that manipulation is usually negative, and in most cases the optimum rule
with a manipulator is different to the one with sincere voters.
