Missing top incomes and tax-benefit microsimulation: evidence from correcting household survey data using tax records data

Using the microsimulation model EUROMOD for Croatia, we compare the results of simulation based on the original survey data (EU-SILC) with those based on the survey data corrected using tax records data and a recent survey correction method. We show that the correction method, although it debiases inequality estimates, may not be able to correct the income structure by source if some income sources are severely under-represented. In Croatia, this is the case for income from capital, property, and contractual work. As a solution, we propose to complement the correction method with an ad hoc pre-correction procedure. The corrections bring the aggregate amount, distribution, and structure of survey income closer to those in the tax data. Consequently, the simulated fiscal instruments become more like those in the tax data. Simulation of a hypothetical tax reform shows the results based on the uncorrected data may be misleading in terms of the estimated budgetary impact and the distributional incidence of the reform.