  We formulate a flexible micro-to-macro kinetic model which is able to explain
the emergence of income profiles out of a whole of individual economic
interactions. The model is expressed by a system of several nonlinear
differential equations which involve parameters defined by probabilities.
Society is described as an ensemble of individuals divided into income classes;
the individuals exchange money through binary and ternary interactions, leaving
the total wealth unchanged. The ternary interactions represent taxation and
redistribution effects. Dynamics is investigated through computational
simulations, the focus being on the effects that different fiscal policies and
differently weighted welfare policies have on the long-run income
distributions. The model provides a tool which may contribute to the
identification of the most effective actions towards a reduction of economic
inequality. We find for instance that, under certain hypotheses, the Gini index
is more affected by a policy of reduction of the welfare and subsidies for the
rich classes than by an increase of the upper tax rate. Such a policy also has
the effect of slightly increasing the total tax revenue.
