  We study the distributions of money in a simple closed economic system for
different types of monetary transactions. We know that for arbitrary and random
sharing but locally conserving money transactions, the money distribution goes
to the Gibb's distribution of statistical mechanics. We then consider the
effects of savings, etc. and see how the distribution changes. We also propose
a new model where the agents invest equal amounts of money in each transaction.
We find that for short time-periods, the money distribution obeys a power-law
with an exponent very close to unity, and has an exponential tail; after a very
long time, this distribution collapses and the entire amount of money goes to a
tiny fraction of the population.
