Data source(s) used: OROS Survey (Employment, earnings and social security contributions): The Oros survey is aimed at producing quarterly indicators on gross wages, other labour costs and total labour cost for firms with at least one employee. To reduce the statistical burden on enterprises, Oros survey uses data from pre-existent statistical surveys and from administrative sources. Oros indicators are estimated by the integration of Social Security data (employers’ social contribution declarations to Inps, the Italian Social Security Institution) and monthly Large firms Survey data (LES). The Oros target population are enterprises and private institutions with employees that, in the reference quarter, have paid wages and salaries subjected to social contributions and classified in the sectors of industry (sections B to F of the Nace Rev. 2) and services (G to N of the Nace Rev. 2). Each quarter, Oros survey releases a provisional estimate on the current quarter and a final estimate related to the same quarter of the preceding year. The provisional estimate is released with a delay of about 70 days after the end of the reference period and can be revised for the next three quarters until the final estimate release, after 12 months. The final estimate is required to incorporate the new information available after the provisional estimate. The discrepancy between the preliminary estimate and the final one depends on many different factors: - quality and completeness of the final version of the administrative micro data improve with respect to the preliminary version; - the annual revision of the LES data referred to the previous year, included in the OROS estimates in the delivery of the first quarter; – updating of structural variables based on other external sources (e.g. Nace Rev. 2 economic activity classification and institutional nature, etc.); - occasional methodological revisions of the indicators’ estimate.