Implicit Social Preferences and Fiscal Reforms: A Microsimulation Analysis for Spain

In this paper, I support the usefulness of using microsimulation models for the normative analysis of real redistribution system. Drawing from three recent works (Bourguignon & Spadaro, 2000, 2005; Oliver & Spadaro, 2004), I propose an application consisting in analyzing how social preferences on inequality have changed since the introduction of the 1999 reforms to the Spanish personal income tax (PIT). The starting point is the observed distribution of a population's gross and disposable incomes and the observed marginal tax rates as computed in standard microsimulation models. I show that, using a set of simplifying assumptions, it is possible to identify the social welfare function that would make the observed marginal tax rate schedule optimal. I apply this methodology to the 1998 and 1999 Spanish PIT, using the Eurostat (ECHP) dataset on the income and socio-demographic characteristics of Spanish households.