  Capital distribution curve is defined as log-log plot of normalized stock
capitalizations ranked in descending order. The curve displays remarkable
stability over periods of time.
  Theory of exchangeable distributions on set partitions, developed for
purposes of mathematical genetics and recently applied in non-parametric
Bayesian statistics, provides probabilistic-combinatorial approach for analysis
and modeling of the capital distribution curve. Framework of the two-parameter
Poisson-Dirichlet distribution contains rich set of methods and tools,
including infinite-dimensional diffusion process.
  The purpose of this note is to introduce framework of exchangeable
distributions on partitions in the financial context. In particular, it is
shown that averaged samples from the Poisson-Dirichlet distribution provide
approximation to the capital distribution curves in equity markets. This
suggests that the two-parameter model can be employed for modelling evolution
of market weights and prices fluctuating in stochastic equilibrium.
