  We conduct a market experiment with human agents in order to explore the
structure of transaction networks and to study the dynamics of wealth
accumulation. The experiment is carried out on our platform for 97 days with
2,095 effective participants and 16,936 times of transactions. From these data,
the hybrid distribution (log-normal bulk and power-law tail) in the wealth is
observed and we demonstrate that the transaction networks in our market are
always scale-free and disassortative even for those with the size of the order
of few hundred. We further discover that the individual wealth is correlated
with its degree by a power-law function which allows us to relate the exponent
of the transaction network degree distribution to the Pareto index in wealth
distribution.
