  We study a model of wealth dynamics [Bouchaud and M\'ezard 2000,
\emph{Physica A} \textbf{282}, 536] which mimics transactions among economic
agents. The outcomes of the model are shown to depend strongly on the
topological properties of the underlying transaction network. The extreme cases
of a fully connected and a fully disconnected network yield power-law and
log-normal forms of the wealth distribution respectively. We perform numerical
simulations in order to test the model on more complex network topologies. We
show that the mixed form of most empirical distributions (displaying a
non-smooth transition from a log-normal to a power-law form) can be traced back
to a heterogeneous topology with varying link density, which on the other hand
is a recently observed property of real networks.
