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Combining Survey and Administrative Data in the Italian EU-SILC Experience: Positive and Critical Aspects

The European Survey on Income and Living Conditions (EU-SILC) is yearly carried out in different EU countries. It aims at providing data for indicators of social cohesion and social exclusion, through collecting a large set of qualitative and quantitative information at individual and household level. In addition, it has to provide both cross-sectional and longitudinal data, to analyse the degree of persistency for the listed indicators. To this purpose, Italy as most of the EU countries adopted a rotational sample design, composed by four rotational groups that have to be followed-up for 4 years. EU-SILC is the natural successor of European Community Household Panel (ECHP) project. Based on the experience from the latter and namely to overcome its quality problems, regulations for EU-SILC are characterized by a preference for output harmonization (a common framework) rather than for an input one (common survey). These regulations configure a flexible environment for National Statistical Offices (NSOs) that carry out this survey whilst settling common guidelines and procedures aiming at minimising cross-country non-comparability. In this context, the Italian experience is innovative with respect to NSOs as well as other national household surveys, for the wide and complex use of administrative registers in different phases of the survey. In this paper we discuss how the use of administrative data allows for improving data quality by (i) ensuring the correct identification and tracing of sample units in order to reduce impact of editing procedures, (ii) editing item non-response, and (iii) reducing under-reporting, memory effect and telescoping. To this purpose we consider two significant steps of the editing procedures that use population register and tax registers. However, the undeniable advantages for the data quality due to combining data from different sources are not exempt from troubles. For instance, timing for accessibility of administrative data, especially for tax data, is not under the strict control of the Italian EU-SILC staff. As a consequence it has an exogenous and deep impact on the management of the whole process, once the fieldwork is completed. Besides, record-linkage and the following set of integration procedures significantly increase the complexity of editing process. All these critical aspects create some difficulties for the timeliness of the data released. Prospectively, any non-negligible modification of fiscal rules, and consequently of the information provided by the administrative registers, could cause a non-repeatability of the current process of data production, and a lack of temporal and cross-countries comparability. In order to discuss positive and critical issues concerning the editing and imputation processes in presence of data obtained through combination of different sources”, the paper proposes an analysis in terms of dimension of quality.