1. A computer-implemented method at a crowdsourcing node in a communications network having a plurality of potential contest participants, the method comprising: storing a data structure in memory the data structure holding a model of a plurality of contests offered by the crowdsourcing node to the potential participants, each contest having a task and a reward; monitoring the plurality of potential contest participants and storing an estimate of a total number of those potential contest participants; using the model and the estimated total number of potential contest participants to control the behavior of the crowdsourcing node.