- Births – A birth is defined as a business that was present in year t, but did not exist in year t-1 or t-2. Births are identified by making a comparison of annual active population files and identifying those present in the latest file, but not the two previous ones. Births do not include entry into the population as a result of mergers, breakups, split offs or other restructuring.
- Deaths – A death is defined as a business that was on the active file in year t but was no longer present on the active file in year t+1 or t+2. This estimate is subject to revision. The deaths data exclude losses to the population as a result of mergers, break-ups, split offs or other restructuring.
- Stock – Recognises activity occurring at any point during the year.