COMBINING SURVEY AND ADMINISTRATIVE DATA IN THE ITALIAN EU-SILC EXPERIENCE: POSITIVE AND CRITICAL ASPECTS National Institute of Statistics - Italy Claudio Ceccarelli, Lucia Coppola, Andrea Cutillo, Davide Di Laurea UNITED NATIONS STATISTICAL COMMISSION and ECONOMIC COMMISSION FOR EUROPE CONFERENCE OF EUROPEAN STATISTICIANS Work session on statistical and data editing Vienna April 2008 Topic (ii): Editing administrative data and combining source

Eu-Silc and It-Silc  Main aims collecting a large set of qualitative and quantitative data at individual and household level providing cross and longitudinal data for measuring income and living condition  Sample design in Italian Eu-Silc (It-Silc) adopting rotational sampling design composed of 4 rotational sub-samples each sub-sample to be followed-up during 4 years  Survey techniques in It-Silc adopting PAPI strategy with interviewer

Administrative data in It-Silc To improve data quality, It-Silc uses:  Population register (PR) to provide correct identification to trace sample units in order to reduce the effect of attrition in calibration estimators  Tax registers (TR) to reduce or remove selective non-response and memory effect and/or telescoping to reduce total non-response effects

Tracing rules and population register  Define target population draw initial sample from register of sampling municipalities  During the fieldwork PR used to combine sample information about household and individuals  After fieldwork completion PR used to integrate incomplete information carried- out from each waves of survey to control the cross sectional and longitudinal consistencies about demographic variables

Tax registers and survey data  Main steps of the integration process Performed at the micro-level (exact matching technique) with survey data Harmonization: sources have ≠ concepts, definitions and classifications for income Example: cooperatives members do perceive  dep. work income for Italian fiscal rules  self-employment income according to EU-SILC regulations Complex statistical data editing to make data consistent:  Income components for year t-1 from the two sources  ILO and self-defined Status in employment in time t Choice of the pertinent income value

Administrative data and total non response  Population and tax registers to reduce the effect of non response Segmentation method by CHAID algorithm Better accuracy of the estimates does not imply greater variability in respect of stratum correction Characteristics from population register: demographic size and territorial domain of the municipality; household size and household head nationality Tax registers: type and amount of income  Important issue in Italy: tax avoidance more frequent in particular sub-groups

Remarks  Positive aspects accuracy completeness comparability macro-level cross and longitudinal coherence  Critical aspects micro-level longitudinal consistency timing for accessibility of tax register imply decrease of timeliness

Future developments  Longitudinal checks of tax registers to increase micro-level longitudinal consistency  Add new rules in cross-sectional editing to increase longitudinal data quality  Introduce selective/macro editing methods to control large variations in cross-sectional data and particular transitions in different waves