There is no formal requirement to collect an existing personal identification number. However, the possibility to uniquely identify each individual in the micro-data is a minimum requirement for monitoring systems (e.g. to ensure that all participants can be re-contacted at a later date in case they are selected as part of a representative sample). As a result, it is recommended that an existing personal identifier, such as the social insurance number, is used since this is:
a. normally straightforward to collect, and
b. can be used to extract relevant data from other administrative registers and thereby reduce the burden of data collection.
However, this is not obligatory and in some cases might conflict with data protection legislation. It is also possible that a unique personal identifier is generated by the monitoring system specifically for the purposes of ESF monitoring. In this case evidence of a robust methodology would be needed for audit purposes.