Participant can be grouped based on their Year of Birth or Year of Start at your organisation.
This method of grouping participant data is most useful when looking at a cohort by age or when they commenced with your organisation and comparing them across a time frame of assessment sets. This way you can track outcomes for whole of organisation strategies by following the same group of participants from year to year.
Both Year of Birth of Year of Start can be set by going to Manage Organisation -> Manage Participants then enter dates for each participant as shown below.

Use Group Creator create group data graphs based on the Year of Birth of Year of Start go to Graphs and Reports -> Group Creator then drag Year of Birth or Year of Start filters across as shown below.

Each year you can create a group based on the same specific Year of Birth or Year of Start. This allows you to track the progress of that specific cohort and analyse the impact of organisation wide strategies.