  We present a new model of collective decision making that captures important
crowd-funding and donor coordination scenarios. In the setting, there is a set
of projects (each with its own cost) and a set of agents (that have their
budgets as well as preferences over the projects). An outcome is a set of
projects that are funded along with the specific contributions made by the
agents. For the model, we identify meaningful axioms that capture concerns
including fairness, efficiency, and participation incentives. We then propose
desirable rules for the model and study, which sets of axioms can be satisfied
simultaneously. An experimental study indicates the relative performance of
different rules as well as the price of enforcing fairness axioms.
