189 research outputs found
Correlation between Risk Aversion and Wealth distribution
Different models of capital exchange among economic agents have been proposed
recently trying to explain the emergence of Pareto's wealth power law
distribution. One important factor to be considered is the existence of risk
aversion. In this paper we study a model where agents posses different levels
of risk aversion, going from uniform to a random distribution. In all cases the
risk aversion level for a given agent is constant during the simulation. While
for a uniform and constant risk aversion the system self-organizes in a
distribution that goes from an unfair ``one takes all'' distribution to a
Gaussian one, a random risk aversion can produce distributions going from
exponential to log-normal and power-law. Besides, interesting correlations
between wealth and risk aversion are found.Comment: 8 pages, 7 figures, submitted to Physica A, Proceedings of the VIII
LAWNP, Salvador, Brazil, 200
Inequalities of wealth distribution in a conservative economy
We analyze a conservative market model for the competition among economic
agents in a close society. A minimum dynamics ensures that the poorest agent
has a chance to improve its economic welfare. After a transient, the system
self-organizes into a critical state where the wealth distribution have a
minimum threshold, with almost no agent below this poverty line, also, very few
extremely rich agents are stable in time. Above the poverty line the
distribution follows an exponential behavior. The local solution exhibits a low
Gini index, while the mean field solution of the model generates a wealth
distribution similar to welfare states like Sweden.Comment: 7 pages, 4 figures, submitted to Physica A, Proceedings of the VIII
LAWNP, Salvador, Brazil, 200
Statistical equilibrium in simple exchange games I
Simple stochastic exchange games are based on random allocation of finite
resources. These games are Markov chains that can be studied either
analytically or by Monte Carlo simulations. In particular, the equilibrium
distribution can be derived either by direct diagonalization of the transition
matrix, or using the detailed balance equation, or by Monte Carlo estimates. In
this paper, these methods are introduced and applied to the
Bennati-Dragulescu-Yakovenko (BDY) game. The exact analysis shows that the
statistical-mechanical analogies used in the previous literature have to be
revised.Comment: 11 pages, 3 figures, submitted to EPJ
Microeconomics of the ideal gas like market models
We develop a framework based on microeconomic theory from which the ideal gas
like market models can be addressed. A kinetic exchange model based on that
framework is proposed and its distributional features have been studied by
considering its moments. Next, we derive the moments of the CC model (Eur.
Phys. J. B 17 (2000) 167) as well. Some precise solutions are obtained which
conform with the solutions obtained earlier. Finally, an output market is
introduced with global price determination in the model with some necessary
modifications.Comment: 15pp. Revised & a reference added. An appeal in Appendix-annex
(section 8; not for publication) also added. Physica A (accepted for
publication
Entropy and equilibrium state of free market models
Many recent models of trade dynamics use the simple idea of wealth exchanges
among economic agents in order to obtain a stable or equilibrium distribution
of wealth among the agents. In particular, a plain analogy compares the wealth
in a society with the energy in a physical system, and the trade between agents
to the energy exchange between molecules during collisions. In physical
systems, the energy exchange among molecules leads to a state of equipartition
of the energy and to an equilibrium situation where the entropy is a maximum.
On the other hand, in the majority of exchange models, the system converges to
a very unequal condensed state, where one or a few agents concentrate all the
wealth of the society while the wide majority of agents shares zero or almost
zero fraction of the wealth. So, in those economic systems a minimum entropy
state is attained. We propose here an analytical model where we investigate the
effects of a particular class of economic exchanges that minimize the entropy.
By solving the model we discuss the conditions that can drive the system to a
state of minimum entropy, as well as the mechanisms to recover a kind of
equipartition of wealth
Wealth redistribution with finite resources
We present a simplified model for the exploitation of finite resources by
interacting agents, where each agent receives a random fraction of the
available resources. An extremal dynamics ensures that the poorest agent has a
chance to change its economic welfare. After a long transient, the system
self-organizes into a critical state that maximizes the average performance of
each participant. Our model exhibits a new kind of wealth condensation, where
very few extremely rich agents are stable in time and the rest stays in the
middle class.Comment: 4 pages, 3 figures, RevTeX 4 styl
Basic kinetic wealth-exchange models: common features and open problems
We review the basic kinetic wealth-exchange models of Angle [J. Angle, Social
Forces 65 (1986) 293; J. Math. Sociol. 26 (2002) 217], Bennati [E. Bennati,
Rivista Internazionale di Scienze Economiche e Commerciali 35 (1988) 735],
Chakraborti and Chakrabarti [A. Chakraborti, B. K. Chakrabarti, Eur. Phys. J. B
17 (2000) 167], and of Dragulescu and Yakovenko [A. Dragulescu, V. M.
Yakovenko, Eur. Phys. J. B 17 (2000) 723]. Analytical fitting forms for the
equilibrium wealth distributions are proposed. The influence of heterogeneity
is investigated, the appearance of the fat tail in the wealth distribution and
the relaxation to equilibrium are discussed. A unified reformulation of the
models considered is suggested.Comment: Updated version; 9 pages, 5 figures, 2 table
Scaling Theory for Migration-Driven Aggregate Growth
We give a comprehensive rate equation description for the irreversible growth
of aggregates by migration from small to large aggregates. For a homogeneous
rate K(i;j) at which monomers migrate from aggregates of size i to those of
size j, that is, K(ai;aj) ~ a^{lambda} K(i,j), the mean aggregate size grows
with time as t^{1/(2-lambda)} for lambda<2. The aggregate size distribution
exhibits distinct regimes of behavior which are controlled by the scaling
properties of the migration rate from the smallest to the largest aggregates.
Our theory applies to diverse phenomena, such as the distribution of city
populations, late stage coarsening of non-symmetric binary systems, and models
for wealth exchange.Comment: 4 pages, 2-column revtex format. Revision to appear in PRL. Various
changes in response to referee comments. Figure from version 1 deleted but is
available at http://physics.bu.edu/~redne
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