The four criteria for assessing class importance apply to irregular aggregate field systems as follows:
- Period (currency): Restricted. Although it is reasonable to assume that there was prolonged use of this monument class, the scarcity of reliable dating evidence and limited number of sites restricts the period of use of this monument class to less than 300 years.
- Rarity: Very rare. There are less than 10 recorded examples of this monument class which can be assigned to the Roman period with any degree of certainty. Further research in areas of the country other than Cornwall may add to this number.
- Diversity (form): Low. There is one main type of irregular aggregate field system on the basis of ground plan morphology.
- Period (representativity): Medium. Irregular aggregate field systems are one of relatively few classes of monument characteristic of the Roman period in Britain. Their occurrence is very localised but they represent the economic basis of life in those areas.
Assigning scores to these criteria following the system set out in the Monument Evaluation Manual, irregular aggregate field systems yield a Class Importance Value of 25. This lies just over one third of the way up the range of possible values (max.= 64), reflecting the rarity, but basic homogeneity, of this monument class. Examples representing the full range of landscape situations and related settlements should be included in the sample of nationally important sites.