  A common economic process is crowdsearch, wherein a group of agents is
invited to search for a valuable physical or virtual object, e.g. creating and
patenting an invention, solving an open scientific problem, or identifying
vulnerabilities in software. We study a binary model of crowdsearch in which
agents have different abilities to find the object. We characterize the types
of equilibria and identify which type of crowd maximizes the likelihood of
finding the object. Sometimes, however, an unlimited crowd is not sufficient to
guarantee that the object is found. It even can happen that inviting more
agents lowers the probability of finding the object. We characterize the
optimal prize and show that offering only one prize (winner-takes-all)
maximizes the probability of finding the object but is not necessarily optimal
for the crowdsearch designer.
