A Simple Characterization of Dynamic Completeness in Continuous Time

I establish a necessary and sufficient condition for the securities' market to be dynamically-complete in a single-commodity, pure-exchange economy with many Lucas' trees whose dividends are geometric Brownian motions. Even though my analysis is based upon the representative-agent version of this economy, the condition depends neither on the utility function of the representative agent, nor on the functional form of her endowment. As a consequence, it characterizes dynamic completeness in this economy even in the presence of many heterogenous agents.