  The dynamic behavior of a multiagent system in which the agent size $s_{i}$
is variable it is studied along a Lotka-Volterra approach. The agent size has
hereby for meaning the fraction of a given market that an agent is able to
capture (market share). A Lotka-Volterra system of equations for prey-predator
problems is considered, the competition factor being related to the difference
in size between the agents in a one-on-one competition. This mechanism
introduces a natural self-organized dynamic competition among agents. In the
competition factor, a parameter $\sigma$ is introduced for scaling the
intensity of agent size similarity, which varies in each iteration cycle. The
fixed points of this system are analytically found and their stability analyzed
for small systems (with $n=5$ agents). We have found that different scenarios
are possible, from chaotic to non-chaotic motion with cluster formation as
function of the $\sigma$ parameter and depending on the initial conditions
imposed to the system. The present contribution aim is to show how a realistic
though minimalist nonlinear dynamics model can be used to describe market
competition (companies, brokers, decision makers) among other opinion maker
communities.
