  We propose a simple statistical-physics-inspired model for the effect of
intrinsic fluctuations on supply and demand in markets. The model consists of
agents that trade in two types of goods of which the total number is separately
conserved. The relative preference of an individual agent for the two types of
goods is determined by a utility that is identical for all agents. Market
supply and demand curves are computed and compared for various motivated
choices of the distribution of goods over the agents. In particular, we compare
the "mean-field" case, in which all agents have the same number of goods and
that is akin to the economics textbook case, to the case of Boltzmann-Gibbs
distributed goods, in which agents have a fluctuating number of goods. We find
that the resulting equilibrium prices are not equal for these two approaches,
especially when a large fraction of the agents can neither buy nor sell.
