  We focus on the problem of how wealth is distributed among the units of a
networked economic system. We first review the empirical results documenting
that in many economies the wealth distribution is described by a combination of
log--normal and power--law behaviours. We then focus on the Bouchaud--M\'ezard
model of wealth exchange, describing an economy of interacting agents connected
through an exchange network. We report analytical and numerical results showing
that the system self--organises towards a stationary state whose associated
wealth distribution depends crucially on the underlying interaction network. In
particular we show that if the network displays a homogeneous density of links,
the wealth distribution displays either the log--normal or the power--law form.
This means that the first--order topological properties alone (such as the
scale--free property) are not enough to explain the emergence of the
empirically observed \emph{mixed} form of the wealth distribution. In order to
reproduce this nontrivial pattern, the network has to be heterogeneously
divided into regions with variable density of links. We show new results
detailing how this effect is related to the higher--order correlation
properties of the underlying network. In particular, we analyse assortativity
by degree and the pairwise wealth correlations, and discuss the effects that
these properties have on each other.
