Data is published by Eurostat according to NACE in 36 different statistical domains (see table 1). The ideal situation would have been that all these statistical domains start using the new classification at the same time in order to allow comparability, cross references and computation of derived statistics. However, this requirement cannot be easily fully met for the following reasons:
- There is always a lag between the reference period and the publication date, and the length of the time lag varies, according to the domain or to the statistics, from one month to more than a year: this causes a long span for the complete implementation of the new classification.
- There is a time dependency between different surveys or different statistics; for instance, National Accounts or Short Term Statistics require for their elaboration weights derived from Structural Business Survey data.
- Domains may have their own constraints: change of base years, coupling with other methodological changes.
As result, within a transition period which goes from 2008 to 2011, some statistical domains will be using NACE Rev. 1 or Rev. 1.1 and others will already use NACE Rev. 2.
Nevertheless, for the main statistical domains, technical measures ensuring a fully coordinated transition from NACE Rev. 1.1 to NACE Rev. 2, like double reporting and back-casting of time series (reconstruction in terms of NACE Rev. 2 of existing statistical time series, currently expressed in terms of NACE Rev. 1 or NACE Rev. 1.1), were foreseen (see table 1).