  A population of voters must elect representatives among themselves to decide
on a sequence of possibly unforeseen binary issues. Voters care only about the
final decision, not the elected representatives. The disutility of a voter is
proportional to the fraction of issues, where his preferences disagree with the
decision.
  While an issue-by-issue vote by all voters would maximize social welfare, we
are interested in how well the preferences of the population can be
approximated by a small committee.
  We show that a k-sortition (a random committee of k voters with the majority
vote within the committee) leads to an outcome within the factor 1+O(1/k) of
the optimal social cost for any number of voters n, any number of issues $m$,
and any preference profile.
  For a small number of issues m, the social cost can be made even closer to
optimal by delegation procedures that weigh committee members according to
their number of followers. However, for large m, we demonstrate that the
k-sortition is the worst-case optimal rule within a broad family of
committee-based rules that take into account metric information about the
preference profile of the whole population.
