  We analyze the optimal size of a congress in a representative democracy. We
take an epistemic view where voters decide on a binary issue with one ground
truth outcome, and each voter votes correctly according to their competence
levels in $[0, 1]$. Assuming that we can sample the best experts to form an
epistemic congress, we find that the optimal congress size should be linear in
the population size. This result is striking because it holds even when
allowing the top representatives to be accurate with arbitrarily high
probabilities. We then analyze real world data, finding that the actual sizes
of congresses are much smaller than the optimal size our theoretical results
suggest. We conclude by analyzing under what conditions congresses of
sub-optimal sizes would still outperform direct democracy, in which all voters
vote.
