  Analytical and numerical studies on many-body stochastic processes with
multiplicative interactions are reviewed. The method of moment relations is
used to investigate effects of asymmetry and randomness in interactions.
Probability distribution functions of the processes generally have similarity
solutions with power-law tails. Growth rates of the system and power-law
exponents of the tails are determined via transcendental equations. Good
agreement is achieved between analytical calculations and Monte Carlo
simulations.
